JP6447486B2 - Discharge control device, gas supply device, and discharge control method - Google Patents

Description

  The present invention relates to a discharge control device, a gas supply device, and a discharge control method.

  2. Description of the Related Art Conventionally, gas reforming apparatuses that reform gas by discharging from an electrode are known. For example, in Patent Document 1, a supply pipe is connected to an exhaust passage through which exhaust from an internal combustion engine passes, and an ozone generation unit that generates ozone by discharge from an electrode is provided in the supply pipe as a gas reformer. In this configuration, the current flowing through the electrode as the voltage is applied is detected by the current detection circuit, and whether or not the discharge from the electrode has occurred is determined based on the detected current value.

Japanese Patent Laying-Open No. 2015-183682

  However, when the current detection accuracy decreases due to noise or the like, for example, the determination accuracy as to whether or not the discharge from the electrode has occurred tends to decrease. In particular, in the configuration in which the current detection circuit is provided in the power supply circuit for applying a voltage to the electrode, noise generated in the power supply circuit is easily included in the detection value of the current detection circuit, and discharge from the electrode has occurred. It becomes difficult to determine whether or not. In this case, there is a concern that the applied voltage to the electrode is too small and no discharge occurs, or that the applied voltage is too large and the power efficiency is reduced during the discharge.

  The present invention has been made in view of the above problems, and an object thereof is to provide a discharge control device, a gas supply device, and a discharge control method that improve power efficiency while reliably reforming a gas. It is in.

  The technical means of the invention for achieving the object will be described below. The reference numerals in parentheses described in the scope of claims and this column disclosing technical means of the invention indicate the correspondence with the specific means described in the embodiment described in detail later. It is not intended to limit the technical scope of the invention.

In order to solve the above-mentioned problem, the first invention disclosed is
A gas reformer (32) provided in a gas passage (31) connected to an exhaust passage (16) through which exhaust gas from the internal combustion engine (10) flows , and reforming the gas by discharge from the electrode (41) ; A discharge control device (60) for controlling operation,
Using the detection results of temperature sensors (37a, 37b) provided on the upstream side and the downstream side of the gas reformer in the gas passage to detect the temperature of the gas, the temperature of the gas flowing out from the gas reformer is determined as the gas temperature. A temperature acquisition unit (S204, S209, S301, S305) acquired as (T);
An increase amount acquisition unit (S210, S306) that acquires an increase amount (ΔT) of the gas temperature using an acquisition result of the temperature acquisition unit;
A voltage setting unit (74) for variably setting a search voltage (Vs) applied to the electrode in order to search for a voltage at which discharge from the electrode occurs;
When the search voltage is set to increase by the voltage setting unit, it is determined whether or not the increase amount of the gas temperature with respect to the predetermined increase amount (Vadd) of the search voltage is larger than a predetermined determination value (A). A temperature determination unit (S211, S307),
A voltage acquisition unit (S215) for acquiring a search voltage when the gas temperature increase amount is larger than a determination value as a discharge start voltage (Vdis) at which discharge is started in the gas reformer;
It has.

  The inventors have obtained the knowledge that when an electric discharge occurs from an electrode, an electron avalanche occurs in an electric field, so that the temperature of the gas around the electrode tends to increase. According to this knowledge, the amount of increase in the gas temperature flowing out from the gas reformer differs depending on whether or not the discharge from the electrode is occurring.

On the other hand, according to the first invention, as the search voltage applied to the electrode increases, it is determined whether or not the increase amount of the gas temperature is larger than the determination value. A voltage whose amount is larger than the determination value can be acquired as a discharge start voltage indicating the start of discharge. In this case, the discharge start voltage can be searched with high precision even if the discharge pressure varies depending on, for example, the gas pressure around the electrode, the individual difference of the gas reformer, or the aging deterioration. For this reason, when gas reforming is performed by a gas reforming device for the purpose of after-treatment of exhaust gas, the fact that gas reforming is not performed despite the application of a discharge start voltage to the electrode, It can be avoided that the power consumption accompanying the voltage application to is excessively large. Therefore, it is possible to improve the power efficiency while reliably reforming the gas.
One disclosed invention is:
A discharge control device (60) for controlling the operation of a gas reforming device (32) for reforming a gas by discharging from an electrode (41),
A temperature acquisition unit (S204, S209, S301, S305) for acquiring the temperature of the gas flowing out from the gas reformer as the gas temperature (T);
A voltage setting unit that variably sets a search voltage (Vs) applied to an electrode in order to search for a voltage at which discharge from the electrode occurs, and determines a search voltage in advance when application of a voltage to the electrode is started. A voltage setting unit (74) for setting the initial voltage (Vbase) obtained;
Whether or not the increase amount (ΔT) of the gas temperature with respect to the predetermined increase amount (Vadd) of the search voltage is larger than a predetermined determination value (A) when the voltage setting unit is set to increase the search voltage. A temperature determination unit (S211, S307) for determining whether
An initial stop unit (S216) for stopping application of the initial voltage to the electrode when the temperature determination unit determines that the amount of increase in the gas temperature is greater than the determination value;
With
The voltage setting unit updates the initial voltage to a voltage smaller by a predetermined value when resuming the application of the voltage to the electrode after the application of the initial voltage is stopped by the initial stop unit.
The temperature determination unit determines whether or not the amount of increase in gas temperature is greater than a determination value when application of a voltage to the electrode is started at an initial voltage.

The second invention disclosed in order to solve the above-described problem is
A gas reformer (32) that generates ozone by reforming the gas by discharge from the electrode (41);
An ozone passage (31) connected to an internal combustion passage (16) extending from the internal combustion engine (10) and supplying ozone generated by the gas reformer to the internal combustion passage;
A temperature sensor (37a) for detecting the temperature of the gas flowing out of the gas reformer;
A control device (60) for controlling the operation of the gas reformer;
Equipped with a,
The control device
A temperature acquisition unit (S204, S209, S301, S305) for acquiring the temperature of the gas flowing out from the gas reformer as the gas temperature (T);
A voltage setting unit that variably sets a search voltage (Vs) applied to an electrode in order to search for a voltage at which discharge from the electrode occurs, and determines a search voltage in advance when application of a voltage to the electrode is started. A voltage setting unit (74) for setting the initial voltage (Vbase) obtained;
Whether or not the increase amount (ΔT) of the gas temperature with respect to the predetermined increase amount (Vadd) of the search voltage is larger than a predetermined determination value (A) when the voltage setting unit is set to increase the search voltage. A temperature determination unit (S211, S307) for determining whether
An initial stop unit (S216) for stopping application of the initial voltage to the electrode when the temperature determination unit determines that the amount of increase in the gas temperature is greater than the determination value;
With
The voltage setting unit updates the initial voltage to a voltage smaller by a predetermined value when resuming the application of the voltage to the electrode after the application of the initial voltage is stopped by the initial stop unit.
The temperature determination unit determines whether or not the amount of increase in gas temperature is greater than a determination value when application of a voltage to the electrode is started at an initial voltage.

  According to the second invention, since the temperature of the gas flowing out from the gas reformer is detected by the temperature sensor, when the voltage applied to the electrode is increased, the amount of increase in the temperature of the gas is acquired. Can do. For this reason, the same effect as the first invention can be obtained.

The third invention disclosed in order to solve the above-described problem is
A discharge control method for controlling the operation of a gas reformer (32) for reforming a gas by discharging from an electrode (41),
The temperature of the gas flowing out from the gas reformer is acquired as the gas temperature (T) (S204, S209, S301, S305),
In order to search for the voltage at which discharge from the electrode occurs, the search voltage (Vs) applied to the electrode is variably set (74),
When starting to apply voltage to the electrode, the search voltage is set to a predetermined initial voltage (Vbase) (74),
If the search voltage is set so as to increase, it is determined whether a predetermined increase amount judgment value increase amount of the gas temperature ([Delta] T) is predetermined for (Vadd) (A) is larger than whether the search voltage (S211, S307) ,
When it is determined that the gas temperature increase amount is greater than the determination value, the application of the initial voltage to the electrode is stopped (S216),
When the application of the voltage to the electrode is resumed after the application of the initial voltage is stopped, the initial voltage is updated to a voltage smaller by a predetermined value (74),
When the application of the voltage to the electrode is started at the initial voltage, it is determined whether or not the increase amount of the gas temperature is larger than the determination value (S211 and S307).

  According to the third invention, the same effect as the first invention is obtained.

The figure which shows the structure of the combustion system in 1st Embodiment. The figure which shows the relationship between gas temperature and ozone concentration. The figure which shows the relationship between the internal pressure of a discharge reactor, and a spark voltage. The figure which shows the structure of a discharge reactor. The flowchart which shows the procedure of an ozone management process. The flowchart which shows the procedure of a search process. The figure which shows the relationship between search voltage, gas temperature, and temperature change when discharge does not occur at the initial voltage. The figure which shows the relationship between the search voltage when a discharge generate | occur | produces with an initial voltage, gas temperature, and a temperature change. The flowchart which shows the procedure of the search process in 2nd Embodiment. The figure which shows the relationship between a search voltage, gas temperature, and a temperature change when discharge generate | occur | produces with a value with a search voltage smaller than an upper limit.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. In addition, not only combinations of configurations explicitly described in the description of each embodiment, but also the configurations of a plurality of embodiments can be partially combined even if they are not explicitly specified unless there is a problem with the combination. .

(First embodiment)
The combustion system shown in FIG. 1 includes an engine 10, an LNT 12, and a DPF 13. The combustion system is mounted on a vehicle, and this vehicle runs using the output of the engine 10 as a drive source. The engine 10 is a compression self-ignition type diesel engine, and light oil that is a hydrocarbon compound is used as a fuel for combustion. An intake passage for supplying air to the engine 10 and an exhaust passage 16 for discharging exhaust from the engine 10 are connected to the engine 10. The exhaust passage 16 is connected to the exhaust side of the engine 10 via an exhaust manifold. The engine 10 corresponds to an internal combustion engine.

  LNT 12 (Lean NOx Traps) is a NOx occlusion reduction catalyst that purifies nitrogen oxides NOx, and is provided in the exhaust passage 16. The DPF 13 (Diesel Particulate Filter) is a particulate collection device that collects particulates contained in the exhaust, and is disposed downstream of the LNT 12. Particulate matter PM (Particulate Matter) is contained in the fine particles collected by the DPF 13. Exhaust gas flowing through the exhaust passage 16 is discharged from the exhaust outlet 16a after passing through both the LNT 12 and the DPF 13. The LNT 12 and the DPF 13 constitute an exhaust purification device.

The combustion system has an ozone supply device 30 that supplies ozone O 3 to the upstream side of the LNT 12 in the exhaust passage 16. If the ozone is supplied to the exhaust passage 16 from the ozone supply device 30, the proportion of NO ₂ by NO in the exhaust by ozone is oxidized to NO ₂ is increased, as a result, improved NOx storage modulus at LNT12 To do. The ozone supply device 30 can shift between a supply state in which ozone is supplied to the exhaust passage 16 and a stop state in which ozone is not supplied.

  The combustion system has a supercharger (not shown). The supercharger includes an exhaust turbine, a rotating shaft, and a compressor. The exhaust turbine is disposed in the exhaust passage 16 of the engine and is rotated by the kinetic energy of the exhaust. The rotating shaft couples the impellers of the exhaust turbine and the compressor to transmit the rotational force of the exhaust turbine to the compressor. The compressor is disposed in the intake passage and compresses intake air to supercharge the engine 10.

  The ozone supply device 30 includes an ozone passage 31 connected to the exhaust passage 16, a discharge reactor 32 that generates ozone by generating discharge with respect to a gas such as air, and an air pump 33 that sends gas to the discharge reactor 32. And an exhaust cutoff valve 34 that shuts off the backflow of exhaust gas in the ozone passage 31. The exhaust passage 16 corresponds to an internal combustion passage to which ozone is supplied from the ozone passage 31.

  The ozone supply device 30 includes a pressure sensor 35 that detects the internal pressure of the ozone passage 31 as a gas pressure, a flow rate sensor 36 that detects a gas flow rate in the ozone passage 31, and temperature sensors 37a and 37b that detect the temperature of the gas. And a humidity sensor 38 for detecting the humidity of the gas and an ozone sensor 39 for detecting ozone. A downstream temperature sensor 37 a provided on the downstream side of the discharge reactor 32 detects the temperature of the gas flowing out from the discharge reactor 32, and an upstream temperature sensor 37 b provided on the upstream side of the discharge reactor 32 is a gas flowing into the discharge reactor 32. Detect the temperature.

  An air pump 33 is provided at the upstream end of the ozone passage 31, and a discharge reactor 32 is provided between the air pump 33 and the exhaust passage 16. The air pump 33 is a centrifugal air pump and is configured by housing an impeller driven by an electric motor in a case. The air pump 33 has a suction port 33a for sucking air, and the suction port 33a is formed in the case. The air pump 33 is a blowing unit that shifts to a blowing state, and can change the blowing amount. The suction port 33 a of the air pump 33 forms the upstream end of the ozone passage 31.

  The discharge reactor 32 is a gas reformer that reforms a gas by generating a discharge, and can also be called an ozone generator or an ozonizer. The discharge reactor 32 of the present embodiment generates ozone from oxygen in the air sent from the air pump 33. In this case, the ozone supply device 30 corresponds to a gas supply device that supplies the gas reformed in the discharge reactor 32 to the exhaust passage 16.

  The discharge reactor 32 includes a housing 42 that forms a flow passage 42a therein, and a plurality of electrodes 41 are disposed in the flow passage 42a. These electrodes 41 have a flat plate shape arranged so as to face each other in parallel, and electrodes 41 to which a high voltage is applied and electrodes 41 having a ground voltage are alternately arranged. Each electrode 41 extends from the upstream side of the discharge reactor 32 toward the downstream side. The gas blown by the air pump 33 flows into the housing 42 of the discharge reactor 32. This gas flows into the flow passage 42 a in the housing 42 and flows through the interelectrode passage 41 a that is a passage between the electrodes 41.

When a voltage is applied to the electrode 41 of the discharge reactor 32, electrons emitted from the electrode 41 collide with oxygen molecules contained in the gas in the interelectrode passage 41a, and two oxygen atoms are generated from the oxygen molecules. The oxygen atoms are combined with other oxygen molecules to generate ozone O ₃ . Here, when an electron collides with an oxygen molecule, two oxygen atoms are generated and two electrons are emitted, and these electrons collide with another oxygen molecule. When the voltage applied to the electrode 41 is sufficiently large, in the discharge reactor 32, an electron avalanche occurs, the number of electrons increases at an accelerated rate, and discharge is started, and the ozone generated with the discharge is discharged. It will flow out of the reactor 32.

  The inventors have found that when the discharge is started in the discharge reactor 32, the temperature of the gas rises sharply in a short time. For example, as shown in FIG. 2, when a voltage high enough to generate a discharge is applied to the electrode 41 at timing ta, the temperature of the gas flowing into the discharge reactor 32 does not change significantly before and after timing ta. Even in this case, the temperature of the gas flowing out from the discharge reactor 32 is rapidly increased from the timing ta. And in the period when discharge has occurred, the temperature of the outflow gas is continuously higher than the temperature of the inflow gas. Further, after a lapse of a minute time since the voltage application to the electrode 41 is started, ozone is generated with the start of discharge, so that the ozone concentration is rapidly increased. The state where the ozone concentration is high is continued during a period in which discharge is occurring.

  Here, the oxygen molecule is only one type of gas molecule contained in the gas, and there are many gas molecules in the discharge reactor 32 that are not decomposed even when electrons collide when an electron avalanche occurs. . Gas molecules that do not decompose when electrons collide oscillate with the collision of electrons and generate heat. When electric discharge is started with the occurrence of an avalanche, the gas temperature rises in a short time because a large number of gas molecules that generate heat exist with the occurrence of an electron avalanche.

When electrons discharged from the electrode 41 collide with nitrogen molecules, two nitrogen atoms are generated from the nitrogen molecules. Then, NO ₂ is produced by the nitrogen atom is bonded to an oxygen molecule. That is, NOx is generated. Further, oxygen atoms generated by the decomposition of oxygen molecules are combined with nitrogen molecules, so that nitrous oxide N ₂ O is generated as laughing gas. Incidentally, when discharge is started, the amount of N ₂ O generated is about 1/200 of the amount of ozone generated.

  In the discharge reactor 32, the likelihood of occurrence of discharge changes according to the internal pressure. According to Paschen's law, as shown in FIG. 3, the relationship between the spark voltage, which is the voltage at which discharge occurs, and the gas pressure is shown by a curve, and when the value on the horizontal axis increases from Xa to Xb, The axis value also increases from Ya to Yb. Here, the value on the horizontal axis is the product of the separation distance between the opposing electrodes 41 and the internal pressure. If the separation distance is constant, the spark pressure increases as the internal pressure increases. In other words, the discharge tends to occur at a low voltage as the internal pressure decreases. Note that the internal pressure of the discharge reactor 32 is substantially the same as the gas pressure detected by the pressure sensor 35.

  As shown in FIG. 4, the electrode 41 includes a base material 44, an electrode wire 45, and a dielectric film 46 described below. The base material 44 has a plate shape made of a dielectric. An electrode wire 45 is provided on the base material 44, and a dielectric film 46 covering the electrode wire 45 is provided on the base material 44. That is, the entire surface of the substrate 44 is covered with the dielectric film 46 so as to enclose the printed electrode wire 45.

  Specifically, among the plurality of electrodes 41 shown in FIG. 4, electrode lines 45 are printed on both surfaces of the substrate 44 except for the electrodes positioned at both ends. The electrode wire 45 has a linear shape extending meandering along the surface of the base material 44 so as to be distributed over the entire surface of the base material 44. In FIG. 4 showing the cross section of the electrode 41, it seems that a plurality of electrode lines 45 are arranged on the same base material 44, but the electrode lines 45 have a shape extending in a branched manner in FIG. The plurality of electrode lines 45 expressed are connected to each other in a plan view. Among the plurality of electrodes 41 shown in FIG. 4, the electrode lines 45 and the dielectric film 46 are provided on one surface of the substrate 44 for the electrodes located at both ends.

  In FIG. 4, the cross-sectional area of the electrode wire 45 is schematically exaggerated, so that a space exists between the dielectric film 46 and the base material 44. However, in reality, such a space does not exist, and the dielectric film 46 is in close contact with the base material 44 in a state of including the electrode wire 45.

  Of the four electrodes 41 shown in FIG. 4, the electrode 41 positioned at the bottom and the electrode 41 positioned above the two are the application electrodes described above. In addition, the electrode 41 located at the top and the electrode 41 located two positions below are the above-described ground electrodes. A pulse voltage is applied to the two electrode lines 45 included in the application electrode. The two electrode lines 45 included in the ground electrode are both grounded. That is, the two electrode lines 45 provided in the same electrode 41 have the same potential. Electrons emitted from the electrode wire 45 of the ground electrode move toward the application electrode through the interelectrode passage 41a. The electrons moving in this way collide with oxygen molecules present in the interelectrode passage 41a, thereby generating ozone.

  Here, contrary to the present embodiment, when a plate-like electrode is used instead of the electrode wire 45, the intensity distribution of the electric field generated in the interelectrode passage 41a becomes uniform. On the other hand, in the present embodiment, since the linear electrode wire 45 is employed, the electric field generated in the interelectrode passage 41 a is concentrated on the electrode wire 45. In the interelectrode passage 41a, a discharge (seed discharge) is generated starting from the portion where the electric field is concentrated in this way, and the discharge is easily induced in the portion where the electrolysis is not concentrated due to the seed discharge. Therefore, discharge in the interelectrode passage 41a can be stably generated without increasing the voltage applied to the electrode wire 45. In this case, the interelectrode passage 41a can also be referred to as a discharge space in which discharge from the electrode 41 occurs.

  Further, in this embodiment, since the dielectric film 46 covering the electrode wire 45 is provided, the electrons that have moved toward the application electrode cause creeping discharge such as movement along the surface of the dielectric film 46 of the application electrode. become. Then, since the opportunity for the discharged electrons to come into contact with the oxygen present in the interelectrode passage 41a increases, the rate at which ozone is generated from oxygen is improved.

  As shown in FIG. 4, the electrode wire 45 included in the ground electrode is connected to the ground, and the electrode wire 45 included in the application electrode is connected to the reactor power supply unit 48. The reactor power supply unit 48 includes a power supply unit 48a such as a battery mounted on the vehicle, and a transformer unit 48b that converts the voltage of the power supply unit 48a. The power supply unit 48a is connected to the electrode wire 45 via the transformer unit 48b. It is connected to the. The transformer 48b can step up or step down the low voltage power supplied from the power source 48a. For example, the voltage of 12V can be boosted to 15 kV, and the boost width can be changed from 100V to 500V.

  The reactor power supply unit 48 has a pulse circuit that generates a pulse voltage from the DC voltage of the power supply unit 48a. The pulse circuit is provided between the power supply unit 48a and the transformer unit 48b, and the transformer unit 48b transforms the pulse voltage. When discharge is started by applying a pulse voltage to the electrode 41, a current corresponding to the pulse voltage flows between the application electrode and the ground electrode. This current includes a lot of noise by repeatedly increasing and decreasing in a short time due to the movement of electric charge due to discharge.

  In addition, the reactor power supply unit 48 includes a switch unit that can stop power supply from the power supply unit 48 a to the electrode 41. The switch part can be switched between an energized state and a cut-off state. When the switch part is in the energized state, a voltage is applied to the electrode 41, and when the switch part is in a cut-off state, no voltage is applied to the electrode 41. .

  The reactor power supply unit 48 may include an AC circuit that generates an AC voltage from the DC voltage of the power supply unit 48a. In this case, the AC circuit is provided between the power supply unit 48a and the transformer unit 48b, and the transformer unit 48b transforms the AC voltage. In addition, in the reactor power supply unit 48, regardless of whether a pulse voltage or an AC voltage is generated, these voltages may be burst voltages.

  Here, in the electrode 41, the base material 44, the electrode wire 45, and the dielectric film 46 are all formed of a dielectric material such as ceramic, and low temperature plasma is generated by discharge using a pulse voltage. In the discharge reactor 32, even if low temperature plasma is generated, the gas does not become higher than, for example, 200 degrees, and it is difficult for the generated ozone to be decomposed by the high temperature gas.

  On the other hand, for example, in a configuration in which the electrode 41 is formed of a metal material, a direct current voltage must be used instead of a pulse voltage in order to generate a discharge, and thermal plasma is generated in the discharge by the direct current voltage. Become. In the discharge reactor 32, the temperature of the gas rises as ozone is decomposed due to the generation of thermal plasma. For this reason, even if ozone is generated with discharge, the ozone is decomposed by heat.

  Returning to FIG. 1, the exhaust cutoff valve 34 is a mechanical or electromagnetically driven on / off valve, and is provided between the discharge reactor 32 and the exhaust passage 16 in the ozone passage 31. The exhaust cutoff valve 34 can be shifted between an open state that allows ventilation and a closed state that blocks ventilation, and the closed state corresponds to the cutoff state. When the exhaust cutoff valve 34 is in the open state, the passage flow rate of the ozone passage 31 is adjusted according to the opening degree of the exhaust cutoff valve 34. The passage flow rate of the ozone passage 31 is maximized when the exhaust cutoff valve 34 is fully open. The exhaust cutoff valve 34 corresponds to an exhaust cutoff unit.

  The pressure sensor 35 is provided between the discharge reactor 32 and the exhaust cutoff valve 34 in the ozone passage 31. Specifically, the pressure sensor 35 is disposed at a position near the discharge reactor 32. In this case, the pressure change accompanying the opening / closing of the exhaust cutoff valve 34 is easily reflected in the detection result of the pressure sensor 35. The pressure sensor 35 corresponds to a pressure detection unit.

  The flow sensor 36 is provided between the air pump 33 and the discharge reactor 32, and can detect the amount of gas discharged from the air pump 33. Specifically, the flow sensor 36 is arranged at a position near the air pump 33. In this case, the detection result of the flow sensor 36 tends to reflect the change in the gas flow rate associated with the driving and stopping of the air pump 33. The flow rate sensor 36 corresponds to a flow rate detection unit.

  The downstream temperature sensor 37 a is provided near the discharge reactor 32 between the discharge reactor 32 and the exhaust cutoff valve 34. The downstream temperature sensor 37a is electrically insulated from the discharge reactor 32 and the power supply unit 48a. For example, the downstream temperature sensor 37a is attached to the ozone passage 31 and the housing 42 via an insulator such as a synthetic resin material. Further, the downstream temperature sensor 37a is electrically isolated by being insulated from the interelectrode passage 41a of the discharge reactor 32. For this reason, the downstream temperature sensor 37a detects the temperature of the gas flowing out from the discharge reactor 32 in a state in which the downstream temperature sensor 37a is not easily affected by the temperature of the piping forming the ozone passage 31, the housing 42, and the electrode 41.

  The upstream temperature sensor 37 b is provided near the discharge reactor 32 between the discharge reactor 32 and the air pump 33. The humidity sensor 38 is disposed between the discharge reactor 32 and the humidity sensor 38 and detects the humidity of the gas flowing into the discharge reactor 32. The ozone sensor 39 is provided between the exhaust shut-off valve 34 and the exhaust passage 16 in the ozone passage 31, and is disposed near the exhaust passage 16.

  In the exhaust passage 16, a mixer 16 b is provided between the ozone passage 31 and the LNT 12. The mixer 16b is a mixing unit that mixes the ozone supplied from the ozone passage 31 and the exhaust gas, and oxidation of NOx in the exhaust gas by ozone is promoted on the downstream side of the mixer 16b.

  The electrical configuration of the combustion system will be described. The combustion system has an ECU 60 as a control device. The ECU 60 includes a processor 61a, a RAM 41b, a memory 61c, and an interface 41d for inputting and outputting information. The memory 61c is a rewritable nonvolatile storage medium and corresponds to a storage unit.

  The ECU 60 controls the injection amount and injection pressure of the fuel injection valve, the supercharging pressure of the supercharger, and the intake air amount to the engine 10 based on the accelerator opening, the engine load, the engine speed, and the like. Here, an accelerator opening sensor 66 is connected to the ECU 60. The accelerator opening sensor 66 is provided in an accelerator pedal operated by a driver, and can detect an operation amount of the accelerator pedal as an accelerator opening. In this case, the accelerator opening is one of the operation parameters acquired based on the operation amount of the accelerator pedal, and the ECU 60 performs output control of the engine 10 based on the operation parameters.

  Connected to the ECU 60 are a pressure sensor 35, a flow sensor 36, a downstream temperature sensor 37a, a humidity sensor 38, an ozone sensor 39, an exhaust temperature sensor 51, an exhaust pressure sensor 52, a NOx sensor 53, a PM sensor 54, and an A / F sensor 55. Has been. The sensors 51 to 55 are provided in the exhaust passage 16. The exhaust temperature sensor 51 is disposed on the upstream side and the downstream side of the LNT 12, and the A / F sensor 55 is disposed on the upstream side of the LNT 12. The exhaust pressure sensor 52 is provided for the DPF 13 and detects a pressure difference between the upstream side and the downstream side of the DPF 13 in the exhaust passage 16. The exhaust pressure sensor 52 can detect the internal pressure of the exhaust passage 16 as the exhaust pressure. In FIG. 1, illustration of electrical connection lines between the sensors 51 to 55 and the ECU 60 is omitted.

  The ECU 60 is connected with an air pump 33, an exhaust cutoff valve 34, and a reactor power supply unit 48 as actuators. The ECU 60 controls the operation of these actuators by outputting a command signal. For example, with respect to the reactor power supply unit 48, the amount of ozone generated and the rate of generation by the discharge reactor 32 are adjusted by controlling the state of voltage application to the electrode 41. In addition, the air pump 33 adjusts the amount of air blown by the air pump by controlling the amount of power supplied to the air pump 33 by duty control. Further, the exhaust cutoff valve 34 adjusts the gas flow rate and gas pressure in the ozone passage 31 by increasing or decreasing the opening degree of the exhaust cutoff valve 34.

  The ECU 60 executes the control program stored in the memory 61c by the processor 61a, thereby constructing the NOx oxidation unit 71, the DPF regeneration unit 72, the collection regeneration unit 63, and the concentration change unit 64 shown in FIG. 4 as functional blocks. To do.

  The ECU 60 includes a NOx oxidation unit 71 that promotes oxidation of NOx in the exhaust, and a DPF regeneration unit 72 that performs DPF regeneration to remove PM collected by the DPF 13. The DPF regeneration unit 72 promotes PM combustion in the DPF 13 by performing a process of increasing the exhaust temperature. Examples of the process for increasing the exhaust temperature include a process for increasing the fuel injection amount in the engine 10 and a process for shifting the ozone supply device 30 to the supply state and supplying ozone to the DPF 13. The NOx oxidation unit 71 performs a process of shifting the ozone supply device 30 to the supply state.

  The ECU 60 also includes a discharge search unit 73 that searches for a discharge start voltage Vdis at which discharge starts in the discharge reactor 32, and a voltage setting unit 74 that can variably set the voltage applied to the electrode 41. Yes. The discharge search unit 73 stores the discharge start voltage Vdis in the memory 61c as the discharge start voltage Vdis, which is as small as possible, among the voltages at which the electrode 41 generates discharge. In the memory 61c, the discharge start voltage Vdis is stored in correspondence with the gas pressure. The voltage setting unit 74 can increase or decrease the voltage applied to the electrode 41 by controlling the operation of the transformer 48b. The voltage setting unit 74 can also stop the application of voltage to the electrode 41 by controlling the operation of the reactor power supply unit 48.

  The ECU 60 performs an ozone management process for managing the ozone generation of the ozone supply device 30. Here, the ozone management process will be described with reference to FIG. This ozone management process is repeatedly executed at a predetermined cycle during the operation period of the engine 10. The ECU 60 has a function of executing the ozone management process by the processor 61 a, and this function corresponds to the discharge search unit 73. The ECU 60 corresponds to a discharge control device, and the procedure of ozone management processing corresponds to a discharge control method.

  In FIG. 5, in step S <b> 101, it is determined whether or not ozone is supplied to the exhaust passage 16. That is, it is determined whether or not the ozone supply device 30 is shifted to the supply state. Here, it is determined whether or not it is necessary to cause the LNT 12 to perform NOx adsorption. If it is necessary to perform NOx adsorption, it is determined that ozone is to be supplied and the process proceeds to step S102. In addition, as a case where LNT12 performs NOx adsorption, a case where the exhaust gas temperature is higher than a predetermined temperature can be cited.

  In step S102, the operation of the air pump 33 is started, and then, in step S103, the exhaust cutoff valve 34 is shifted to the open state. In this case, the output of the air pump 33 is set to the maximum, and the exhaust cutoff valve 34 is set to a fully open state. In step 104, the discharge start voltage Vdis stored in the memory 61c is read, and this discharge start voltage Vdis is set as a generated voltage V for generating ozone in the discharge reactor 32. In this case, the voltage setting unit 74 is set so that the applied voltage to the electrode 41 becomes the generated voltage V. In step S104, the gas pressure is acquired based on the detection signal of the pressure sensor 35, and the discharge start voltage Vdis corresponding to the gas pressure is read from the memory 61c.

In step S <b> 105, the generated voltage V is applied to the electrode 41 by operating the reactor power supply unit 48. Here, the gas pressure is acquired based on the detection signal of the pressure sensor 35, and in step S106, it is determined whether or not the ozone flowing through the ozone passage 31 downstream from the discharge reactor 32 is insufficient from the memory 61c. Here, the ozone concentration of the gas flowing into the exhaust passage 16 from the ozone passage 31 is calculated based on the detection signal of the ozone sensor 39, and it is determined whether or not the ozone concentration is smaller than a reference value. When the ozone concentration is smaller than the reference value, it is determined that ozone is insufficient due to no discharge in the discharge reactor 32, and the process proceeds to step S107. In addition, after the voltage application to the electrode 41 is started in step S105, the determination process of step S106 is performed after waiting for the time required for the gas flowing out from the discharge reactor 32 to reach the ozone sensor 39.

  In step S107, the generated voltage V is increased in order to generate a discharge in the discharge reactor 32. Here, the generated voltage V is increased by the increase value Va by controlling the operation of the transformer 48b. In this case, the voltage setting unit 74 performs voltage setting so that the voltage applied to the electrode 41 becomes a new generated voltage V. As a result, discharge is more likely to occur in the discharge reactor 32 as much as the generated voltage V increases. After increasing the generated voltage V, the process returns to step S106, and it is determined again whether ozone is insufficient. In this case, steps S106 and S107 are repeated until discharge occurs in the discharge reactor 32. Similarly to step S105, after performing the process of step S107, after waiting for the time required for the gas flowing out from the discharge reactor 32 to reach the ozone sensor 39, the determination process of step S106 is performed.

  When ozone is not supplied to the exhaust passage 16 in step S101, the process proceeds to step S108, and whether or not the engine 10 is idling based on the engine speed, the target injection amount, the detection signal of the accelerator opening sensor 66, and the like. Determine. In step S109, the exhaust pressure is acquired based on the detection signal of the exhaust pressure sensor 52, and it is determined whether or not the exhaust pressure is smaller than a predetermined reference value. Here, it is determined as YES when the exhaust pressure is smaller than the reference value for a predetermined time. As a case where YES is determined, there is a case where the vehicle is traveling at a low speed or a high speed while the speed change is small. For example, the reference value is set to a value of the exhaust pressure such that the exhaust does not flow backward from the exhaust passage 16 to the ozone passage 31 when the output of the air pump 33 is maximized.

  When one of steps S108 and S109 is YES, the process proceeds to step S110, and a search process for searching for the discharge start voltage Vdis is performed. The search process will be described with reference to FIG.

  In FIG. 6, in step S201, the operation of the air pump 33 is started, and then, in step S202, the exhaust cutoff valve 34 is shifted to an open state. In step S203, the gas pressure is acquired based on the detection signal of the pressure sensor 35. In step S204, the temperature of the gas flowing out from the discharge reactor 32 is set as the gas temperature T based on the detection signal of the downstream temperature sensor 37a. get. The gas temperature T acquired in step S204 is the temperature of the gas flowing out of the discharge reactor 32 when no voltage is applied to the electrode 41.

  After the operation of the air pump 33 is started and the exhaust cutoff valve 34 is shifted to the open state, the acquisition process of steps S203 and S204 is performed after waiting until the air blow by the air pump 33 is stabilized. Further, after the air flow is stabilized, the acquisition of the gas pressure and the gas temperature T is performed a plurality of times in these steps S203 and S204. For this reason, the acquisition accuracy of the gas pressure and the gas temperature T before the discharge is started is enhanced.

  Here, with respect to the air pump 33, an air volume as small as possible is calculated based on the exhaust pressure within a range in which no backflow of exhaust gas from the exhaust passage 16 to the ozone passage 31 occurs, and an output is set so as to be this air volume. Here, the search process is repeatedly performed, and the opening degree of the exhaust cutoff valve 34 is set so that the gas pressure becomes a value different from the previous search process. As a result, a plurality of discharge start voltages Vdis corresponding to different gas pressures are stored in the memory 61c.

  In step S205, a search voltage Vs for searching for the discharge start voltage Vdis is set to a predetermined initial voltage Vbase, and in step S206, an increase amount when the search voltage Vs is increased is set as an additional value Vadd. . In step S205, the voltage setting unit 74 sets the voltage so that the applied voltage to the electrode 41 becomes the search voltage Vs.

  The initial voltage Vbase and the additional value Vadd are set based on the gas temperature and gas pressure in the ozone passage 31. Here, inside the discharge reactor 32, the higher the gas temperature, the smaller the voltage required for discharge, and the smaller the gas pressure, the smaller the voltage required for discharge. Therefore, for example, the initial voltage Vbase and the additional value Vadd are set to a smaller value as the gas temperature is higher, and the initial voltage Vbase and the additional value Vadd are set to a smaller value as the gas pressure is decreased. In the present embodiment, the initial voltage Vbase is set to 8 kV, for example, and the additional value Vadd is set to 0.5 kV, for example. Note that the discharge start voltage Vdis searched in the previous search process may be set as the initial voltage Vbase.

  In step S207, a counter n indicating the number of searches is set to n = 0. In step S208, application of the search voltage Vs to the electrode 41 is started by operating the reactor power supply unit 48.

  In step S209, the gas temperature T is acquired based on the detection signal of the downstream temperature sensor 37a. The gas temperature T acquired in step S <b> 208 is the temperature of the gas flowing out from the discharge reactor 32 when a voltage is applied to the electrode 41. In step S210, a value obtained by subtracting the gas temperature T acquired in step S204 from the gas temperature T acquired in step S209 is calculated as the change temperature ΔT. The change temperature ΔT corresponds to the amount of increase.

  In step S211, it is determined whether or not the change temperature ΔT is larger than a determination value A indicating the start of discharge. Here, the determination value A is set based on the gas flow rate, gas pressure, and the like of the ozone passage 31 using data obtained by tests, simulations, and the like. Here, even if the gas temperature T increases with the start of discharge, the amount of increase tends to decrease as the gas flow rate increases. In addition, the lower the gas pressure, the lower the probability that electrons collide with molecules, and the amount of increase in gas temperature T accompanying the start of discharge tends to be small. Therefore, for example, the determination value A is set to a smaller value as the gas flow rate is larger, and the determination value A is set to a smaller value as the gas pressure is smaller.

  After starting application of the search voltage Vs in step S208, the determination process in step 211 is performed after waiting for the time required for the gas flowing out from the discharge reactor 32 to reach the downstream temperature sensor 37a as a standby time. . In this case, in steps S209 and S210, the gas temperature T and the change temperature ΔT are acquired a plurality of times during the standby time. For this reason, the acquisition accuracy of the gas temperature T and the change temperature ΔT after the application of the search voltage Vs is started is improved.

  When the change temperature ΔT is not greater than the determination value A, the process proceeds to step S212, and the counter n is incremented. In step S213, the search voltage Vs is increased using the initial voltage Vbase, the additional value Vadd, and the counter n. Specifically, a value obtained by adding the product of the additional value Vadd and the counter n to the initial voltage Vbase is calculated, and this calculated value is set as the search voltage Vs. In this case, the voltage setting unit 74 performs voltage setting so that the voltage applied to the electrode 41 becomes the new search voltage Vs.

  After the process of step S213, the processes of steps S209 to S211 are performed again. In this case, until the change temperature ΔT is determined to be larger than the determination value A in step S211, the search voltage Vs is increased stepwise with the amount to be increased as the additional value Vadd.

  In step S211 performed after the process of step S213, a value obtained by subtracting the gas temperature T acquired in the process of the previous step S210 from the gas temperature T acquired in the process of the present step S210 is a change temperature. Calculated as ΔT. Further, after the search voltage Vs is increased in step S213, after the application of the search voltage Vs is started in step S208, the determination process in step S211 is performed after waiting for the standby time. In steps S209 and S210, the gas temperature T and the change temperature ΔT are acquired a plurality of times.

  When the change temperature ΔT is larger than the determination value A in step S211, it is determined that the discharge is started in the discharge reactor 32, and the process proceeds to step S214. In step S214, it is determined whether or not n = 0 for the counter n. If n = 0 is not satisfied, the process proceeds to step S215, where the current search voltage Vs is set as the discharge start voltage Vdis and associated with the gas pressure acquired in step S203 and the gas temperature in which discharge has not occurred acquired in step S204. And stored in the memory 61c. In step S215, the application of the search voltage Vs to the electrode 41 is stopped by operating the reactor power supply unit 48.

  Here, the case where n is not 0 is a case where the change temperature ΔT does not become larger than the determination value A even when the initial voltage Vbase is applied to the electrode 41 as the search voltage Vs, as shown in FIG. In this case, after the voltage application to the electrode 41 is started at the timing ta, the search voltage Vs is increased by the additional value Vadd until the change temperature ΔT becomes larger than the determination value A. Then, the gas temperature T starts to rise at the timing tb that is set to such a large value that the search voltage Vs is discharged, and the change temperature ΔT becomes larger than the determination value A. In addition, since the standby time is secured before the determination process of step S211 is performed, the search voltage Vs is not changed and is held for the holding time Th.

  Returning to the description of FIG. 6, if it is determined in step S214 that n = 0 for the counter n, it is determined that discharge has occurred at the initial voltage Vbase, and the process proceeds to step S216. When the discharge occurs at the initial voltage Vbase, the discharge may occur at an applied voltage lower than the initial voltage Vbase. Therefore, in step S216, voltage supply to the electrode 41 is stopped by stopping power supply from the reactor power supply unit 48, and in step S217, the search voltage Vs is set to a voltage smaller than the initial voltage Vbase. Here, the search voltage Vs is decreased by the reduction value Vcut from the initial voltage Vbase. In this case, the voltage setting unit 74 performs voltage setting so that the voltage applied to the electrode 41 becomes the new search voltage Vs. The reduction value Vcut is set based on the ozone temperature, gas pressure, etc. of the ozone passage 31 as in the case of the initial voltage Vbase and the additional value Vadd. In the present embodiment, the reduction value Vcut is set to 1.5 kV, which is larger than the additional value Vadd, for example.

  After step S217, steps S208 to S215 are performed. Here, after the voltage application is stopped in step S216, after waiting for the time required for the gas temperature T, which has risen as a result of the discharge to start at the initial voltage Vbase, to decrease and stabilize, the standby time is set, and then step S208 is performed. The voltage application process is performed. Thus, by waiting until the gas temperature T becomes stable, the change in the gas temperature T when the discharge is started again becomes clear. As a result, even when the mode decreases the search voltage Vs and searches for the discharge start voltage Vdis again, the search accuracy is unlikely to decrease.

  The ECU 60 has a function of executing the processes of steps S203, S204, S208, S209, S211, S215, and S216, and the function of executing the process of step S203 corresponds to the pressure acquisition unit. The function of executing the processes of steps S204 and S209 corresponds to the temperature acquisition unit, the function of executing the process of step S208 corresponds to the application executing unit, and the function of executing the process of step S211 corresponds to the temperature determining unit. The function for executing the process of step S215 corresponds to the storage execution unit, and the function for executing the process of step S216 corresponds to the initial stop unit.

  Here, when it is determined in step S214 that n = 0, the discharge is started by applying the initial voltage Vbase to the electrode 41 as the search voltage Vs as shown in FIG. In this case, at the timing ta when the application of the search voltage Vs to the electrode 41 is started, the gas temperature T starts to rise and the change temperature ΔT becomes larger than the determination value A. Then, the search voltage Vs is secured for the holding time Th, and thereafter, the application of the search voltage Vs to the electrode 41 is stopped for the stop time Toff. This stop time Toff has a length corresponding to the standby time secured before the voltage application process of step S208 is performed after steps S216 and S217.

  The search voltage Vs that is smaller than the initial voltage Vbase by the reduction value Vcut is applied to the electrode 41 at the timing tc when the stop time Toff has elapsed since the application of the search voltage Vs was stopped. Thereby, the search for the discharge start voltage Vdis is started again. FIG. 8 illustrates an example in which discharge is started after the search voltage Vs is increased in a plurality of stages in the re-search of the discharge start voltage Vdis. In this case, the gas temperature T starts to rise at the timing td set to a value large enough to cause the discharge of the search voltage Vs, and the change temperature ΔT becomes larger than the determination value A.

  Here, when the discharge is generated by applying the initial voltage Vbase to the electrode 41 as the search voltage Vs, the voltage application to the electrode 41 is not stopped, but the search is performed while the voltage application to the electrode 41 is continued. A method of decreasing the voltage Vs step by step can be considered. In contrast, when the search voltage Vs is decreased, the inventors maintain the discharge even when the search voltage Vs is reduced beyond the voltage at which the discharge starts as the search voltage Vs increases. I got the knowledge that. That is, the inventors have found that hysteresis occurs in the relationship between the voltage applied to the electrode 41 and the discharge. For this reason, in the method of reducing the search voltage Vs, even if a voltage at which the discharge ends can be acquired, there is a concern that when the voltage is applied to the electrode 41 as the generated voltage V, the discharge is not started. The

  The operational effects of the first embodiment described so far will be described below.

  According to the first embodiment, whether or not the change temperature ΔT of the gas temperature T according to the increase in the search voltage Vs is larger than the determination value A is determined in step S211, so that the discharge is started by the search voltage Vs. A search for voltage Vdis is performed. In this case, even if the discharge generation voltage differs due to gas pressure, gas flow rate, individual differences of the discharge reactor 32, aging deterioration of the discharge reactor 32, etc., the voltage can be obtained with high accuracy as the discharge start voltage Vdis. . Therefore, when ozone is generated by the discharge reactor 32 for the purpose of oxidation of NOx in the exhaust passage 16 or the like, the discharge does not start even though the discharge start voltage Vdis is applied to the electrode as the generated voltage V. Can be prevented from being generated. Further, in this case, since the generation voltage V is excessively high, power consumption with respect to the generation amount of ozone is large, and waste of power can be suppressed. As described above, it is possible to improve the power efficiency while reliably reforming the gas flowing into the discharge reactor 32.

  Note that NOx in the exhaust of the engine 10 is subject to exhaust emission control and is expected to become more severe year by year. As a countermeasure, in this embodiment, the LNT 12 is mounted on the vehicle as a post-processing device. Here, in addition to the LNT 12, the diesel engine after-treatment device includes urea SCR (Selective Catalytic Reduction), and the gasoline engine after-treatment device includes a three-way catalyst. In these post-treatment devices, the exhaust temperature plays an important role in purifying NOx, and the NOx purification catalyst is less likely to have a high activity if the exhaust gas does not reach a certain temperature. Performance is hard to be demonstrated. For this reason, it is an important issue to prevent the exhaust gas temperature from becoming low for future NOx purification.

  When this problem is further analyzed, the NOx purification catalyst is not highly active, which is why it is difficult to oxidize NO necessary in the process of NOx purification by the NOx purification catalyst, and the exhaust temperature is low. Technology that oxidizes NO in a state becomes an important technology. The discharge reactor 32 generates ozone from oxygen molecules, and can generate ozone using air as a raw material. In addition, ozone is a useful technique as a countermeasure for a low exhaust temperature because ozone can directly react with NO and oxidize NO even at low temperatures.

  Further, as described above, since the generated voltage V can be made as small as possible by searching for the discharge start voltage Vdis, it is possible to suppress an increase in the size of the discharge reactor 32 and the reactor power supply unit 48. This is because the larger the voltage applied to the electrode 41, the larger the insulation structure applied to the discharge reactor 32 and the reactor power supply section 48, and the larger the transformer section 48b for generating a high voltage. . Furthermore, since the voltage required for discharge varies depending on the gas temperature, gas pressure, gas composition, and variations in the discharge reactor 32 and the reactor power supply unit 48, a higher voltage is set to ensure discharge. For this reason, the insulation requirement with respect to the discharge reactor 32 and the reactor electric power feeding part 48 becomes high, and these discharge reactor 32 and the reactor electric power feeding part 48 will enlarge.

  According to the first embodiment, when searching for the discharge start voltage Vdis, the search voltage Vs is increased stepwise, so that the search voltage Vs can be held for the holding time Th. For this reason, it can be avoided that the search voltage Vs is increased at a timing before the occurrence of the discharge is reflected in the change temperature ΔT, even though the discharge starts to occur at the current search voltage Vs. . In this case, the smallest possible voltage among the voltages capable of generating discharge is searched for as the discharge start voltage Vdis, so that it is possible to reduce power consumption relative to the amount of ozone generated.

  According to the first embodiment, since the initial voltage Vbase is started when searching for the discharge start voltage Vdis, for example, the search time can be shortened compared to a configuration in which the search voltage Vs starts from “0”. Further, in the configuration in which the search voltage Vs is increased stepwise as in the present embodiment, the search accuracy is improved as the additional value Vadd is decreased, but the search time is increased as the additional value Vadd is decreased. On the other hand, by setting the initial voltage Vbase as high as possible, the search accuracy can be improved and the search time can be prevented from being prolonged.

  According to the first embodiment, when discharge is generated by applying the initial voltage Vbase to the electrode 41 as the search voltage Vs, the search voltage Vs is decreased after the application of the search voltage Vs to the electrode 41 is temporarily stopped. In this state, the application of the search voltage Vs to the electrode 41 is resumed. For this reason, for example, unlike the case where the search voltage Vs is decreased without stopping the application of the search voltage Vs to the electrode 41, the hysteresis generated in the relationship between the discharge and the voltage can be ignored. Therefore, it can suppress that the search precision of the discharge start voltage Vdis falls with the reduction | decrease of the search voltage Vs.

  According to the first embodiment, the discharge start voltage Vdis searched for by the search process is stored in the memory 61c in correspondence with the gas pressure. For this reason, even if the voltage at which discharge starts changes according to the gas pressure, by selecting the discharge start voltage Vdis according to the gas pressure as the generated voltage V, oxidation of NOx in the exhaust passage 16 and the like are performed. The target ozone generation can be performed reliably.

  According to the first embodiment, when the exhaust pressure is smaller than the reference value, the search process in step S110 is performed, so that the output of the air pump 33 can be suppressed as small as possible. When the exhaust pressure is so low that exhaust does not flow back through the ozone passage 31, the gas pressure in the ozone passage 31 decreases as the output of the air pump 33 decreases. In this case, since the voltage at which discharge occurs in the discharge reactor 32 tends to be small, the high voltage applied to the electrode 41 from the reactor power supply section 48 can be reduced. As a result, it is possible to reduce power consumption and increase safety when generating high voltage in the reactor power supply unit 48.

  According to the first embodiment, when the engine 10 is in the idling state, the search process of step S110 is performed, so that the search accuracy of the discharge start voltage Vdis can be increased. This is because when the engine 10 is in the idling state, the change in the gas pressure in the ozone passage 31 is small and the gas temperature T is difficult to change due to the small change in the exhaust pressure.

(Second Embodiment)
In the first embodiment, the search voltage Vs is increased step by step when searching for the discharge start voltage Vdis. In the second embodiment, the search voltage Vs is continuously increased. In the present embodiment, the search process will be described with reference to FIGS. 9 and 10 with a focus on differences from the first embodiment.

  In FIG. 9, in step S301, a preparation process for searching for the discharge start voltage Vdis is performed. Here, the same processing as steps S201 to S205 of the first embodiment is performed. For this reason, the gas supplied from the air pump 33 flows through the ozone passage 31 before the process of step S <b> 302 is performed. Further, the search voltage Vs is set to the initial voltage Vbase.

  In step S302, the increase amount per unit time is set as the increase rate B when the search voltage Vs is continuously increased. The increase rate B is set based on the current gas temperature T, gas pressure, gas flow rate, etc. of the ozone passage 31. For example, as the gas flow rate increases, the amount of increase in the gas temperature T accompanying the occurrence of discharge decreases, and the determination accuracy when determining the occurrence of discharge using the change temperature ΔT tends to decrease. For this reason, the increase rate B is set to be smaller as the gas flow rate is larger and the determination accuracy of the occurrence of discharge is less likely to decrease. Further, a value obtained by dividing the additional value Vadd in the first embodiment by the holding time Th may be set as the increase rate B.

  In step S303, the application of the search voltage Vs to the electrode 41 is started as in step S208 of the first embodiment. In step S304, the search voltage Vs starts increasing at an increase rate B. In steps S305 to S307, the same processing as in steps S209 to S211 of the first embodiment is performed. If the change temperature ΔT is larger than the determination value A in step S307, the process proceeds to step S308.

  In step S308, the search voltage Vs at the excess timing when the change temperature ΔT is greater than the determination value A is acquired. Here, the search voltage Vs at the excess timing is calculated based on the elapsed time from the application start of the search voltage Vs to the excess timing, the search voltage Vs, and the increase rate B. In step S309, the search voltage Vs acquired in step S308 is set as the discharge start voltage Vdis.

  When the gas temperature T is not greater than the determination value A in step S307, the process proceeds to step S310, and it is determined whether or not the search voltage Vs is greater than a predetermined upper limit value Vmax. The upper limit value Vmax is a value obtained by a test or the like, and if the discharge reactor 32 is operating normally, the probability of occurrence of discharge is a very high value. When the search voltage Vs is not greater than the upper limit value Vmax, the processes of steps S305 to S307 are performed assuming that the search voltage Vs is allowed to increase. On the other hand, if the search voltage Vs is greater than the upper limit value Vmax, it is determined that an abnormality has occurred in the discharge reactor 32 and the process proceeds to step S311.

  In step S311, the application of the search voltage Vs to the electrode 41 is stopped as in step S216 of the first embodiment, assuming that the increase in the search voltage Vs is not allowed. In step S312, a notification process is performed. In the notification process, a process for causing the display device of the instrument panel to display that an abnormality has occurred in the discharge reactor 32 and a process for outputting a notification sound from the speaker are performed.

  Here, when it is determined in step S307 that the change temperature ΔT is larger than the determination value A, as shown in FIG. 10, the discharge occurs when the search voltage Vs is smaller than the upper limit value Vmax. In this case, the gas temperature T starts to rise at the timing te when the search voltage Vs reaches a value large enough to cause discharge, and the change temperature ΔT becomes larger than the determination value A.

  According to the second embodiment, when searching for the discharge start voltage Vdis, the search voltage Vs is continuously increased. Therefore, the search voltage Vs at which discharge has started can be detected with high accuracy. For this reason, the search voltage Vs as small as possible can be acquired as the discharge start voltage Vdis. Therefore, when the gas is reformed in the discharge reactor 32, the power consumption with respect to the amount of ozone generated can be reduced.

(Other embodiments)
Although a plurality of embodiments of the present invention have been described above, the present invention is not construed as being limited to these embodiments, and various embodiments and combinations can be made without departing from the scope of the present invention. Can be applied.

  As a first modification, the downstream temperature sensor 47 a may be provided inside the discharge reactor 32 as long as it is electrically insulated from the discharge reactor 32. For example, the flow passage 42a of the housing 42 is disposed at a position that is not the interelectrode passage 41a. That is, the discharge reactor 32 is disposed at a position other than the discharge space. Thereby, the structure which the downstream temperature sensor 47a was electrically isolated from discharge space is realizable.

  As a second modification, the discharge reactor 32 may not include a plurality of pairs of the electrodes 41 but may include only one pair of the electrodes 41. The electrode 41 is not formed by a combination of a plurality of members such as the base material 44, the electrode wire 45, and the dielectric film 46, but one electrode 41 may be formed by one plate material.

  As a third modification, the voltage application to the electrode 41 may be stopped every time the search voltage Vs is increased in the search process of the first embodiment. Even in this case, it is possible to search for the discharge start voltage Vdis.

  As a fourth modification, the initial voltage Vbase, the additional value Vadd, the reduction value Vcut, the increase value Va, and the upper limit value Vmax may be predetermined values. That is, it is good also as a structure which these values do not change according to the gas pressure of the ozone channel | path 31, gas flow rate, etc. Further, the additional value Vadd is not set to the same value without being changed until the discharge start voltage Vdis is searched, but may be changed and set to a different value until the discharge start voltage Vdis is searched. .

  As a fifth modification, the initial voltage Vbase may be set to “0” in the search process of the second embodiment. Even in this case, the search for the discharge start voltage Vdis can be performed by continuously increasing the search voltage Vs at the increase rate B.

  As a sixth modification, the pressure sensor 35 of the ozone passage 31 may be provided upstream of the discharge reactor 32 instead of being provided downstream of the discharge reactor 32, and may be provided inside the discharge reactor 32. It may be done. In any case, the pressure of the gas flowing out from the discharge reactor 32 can be calculated or estimated based on the detection result of the pressure sensor 35.

  As a modified example 7, even when the exhaust pressure is not smaller than the reference value in step S109, the search process may be performed as long as the change mode of the exhaust pressure is stable.

  As a modified example 8, the search process may be performed when the operation of the engine 10 is stopped, such as an idling stop state. In this case, by driving the air pump 33 and moving the exhaust shut-off valve 34 to the open state, it is possible to acquire the change mode of the gas temperature T by the downstream temperature sensor 37a, so that the discharge is performed based on the change temperature ΔT. Can be detected.

  As a modification 9, in the search process of the first embodiment, an additional value Vadd that increases the search voltage Vs and a search voltage Vs that serves as a reference for determining whether or not the change temperature ΔT is greater than the determination value A. The amount of increase may be different. For example, each time the search voltage Vs is increased stepwise, the temperature determination whether the change temperature ΔT is larger than the determination value A is not performed, but after the search voltage Vs is increased stepwise a plurality of times. The temperature is determined.

  As a tenth modification, the function provided by the processor 61a of the ECU 60 can be provided by hardware and software different from those described above, or a combination thereof. For example, in a vehicle in which the ECU 60 is omitted, a control circuit such as a control circuit of the vehicle control ECU may execute part or all of the ozone management process and the search process. Furthermore, each function may be provided by hardware and software different from those described above, or a combination thereof. Further, various non-transitional tangible storage media such as a flash memory and a hard disk can be adopted as the memory 61c for storing a program executed by the processor 61a.

  As a modified example 11, the ozone passage 31 may be connected to an intake passage that performs intake to the engine 10. In this configuration, ozone generated in the discharge reactor 32 is supplied to the intake passage, so that the ignitability of fuel in the engine 10 is easily improved. In this case, the intake passage corresponds to the internal combustion passage.

  As a modified example 12, the engine 10 included in the combustion system may be a gasoline engine instead of a diesel engine as long as it is an internal combustion engine.

  As a modified example 13, the combustion system configured to include the discharge reactor 32 is not limited to an on-board internal combustion engine, and may include an internal combustion engine mounted on a ship, a railway vehicle, an aircraft, or the like. Moreover, you may have the internal combustion engine for electric power generation.

As a modification 14, the discharge reactor 32 may not be included in the combustion system having the engine 10, but may be included in, for example, a medical device for supplying laughing gas. This is because nitrous oxide N ₂ O is generated in addition to ozone as the gas is reformed in the discharge reactor 32 as described above.

DESCRIPTION OF SYMBOLS 10 ... Engine (internal combustion engine), 16 ... Exhaust passage, (Internal combustion passage), 30 ... Ozone supply device (gas supply device), 32 ... Discharge reactor (gas reformer), 41 ... Electrode, 60 ... ECU (discharge control) apparatus),
74: Voltage setting unit, A: Determination value, T: Gas temperature, ΔT: Change temperature (increase amount), V: Search voltage, Vadd: Additional value (increase amount), Vbase: Initial voltage, Vdis: Discharge start voltage.

Claims (11)

A gas reformer (32) provided in a gas passage (31) connected to an exhaust passage (16) through which exhaust gas from the internal combustion engine (10) flows , and reforming the gas by discharge from the electrode (41) ; A discharge control device (60) for controlling operation,
The temperature of the gas flowing out from the gas reformer using the detection results of the temperature sensors (37a, 37b) provided on the upstream side and the downstream side of the gas reformer in the gas passage for detecting the temperature of the gas. A temperature acquisition unit (S204, S209, S301, S305) that acquires the gas temperature (T) as
An increase amount acquisition unit (S210, S306) for acquiring an increase amount (ΔT) of the gas temperature using an acquisition result of the temperature acquisition unit;
A voltage setting unit (74) for variably setting a search voltage (Vs) applied to the electrode in order to search for a voltage at which discharge from the electrode occurs;
When the search voltage is set to increase by the voltage setting unit, or greater than said predetermined increase amount of the search voltage determination value increase amount of the gas temperature is predetermined for (Vadd) (A) A temperature determination unit (S211, S307) for determining whether or not,
A voltage acquisition unit (S215) that acquires the search voltage when the gas temperature increase amount is larger than the determination value as a discharge start voltage (Vdis) at which discharge is started in the gas reformer;
A discharge control device comprising: The voltage setting unit sets the search voltage to a predetermined initial voltage (Vbase) when starting to apply a voltage to the electrode,
The temperature determination unit, when the application of a voltage to the electrode is started by the initial voltage, to claim 1 increased the amount of the gas temperature is to determine greater or not than the determination value The discharge control device described. An initial stop unit (S216) for stopping application of the initial voltage to the electrode when the temperature determination unit determines that the amount of increase in the gas temperature is greater than the determination value;
The voltage setting unit is configured to update the initial voltage to a voltage smaller by a predetermined value when the application of the voltage to the electrode is resumed after the application of the initial voltage is stopped by the initial stop unit. The discharge control device according to claim 2 . A discharge control device (60) for controlling the operation of a gas reforming device (32) for reforming a gas by discharging from an electrode (41),
A temperature acquisition unit (S204, S209, S301, S305) for acquiring the temperature of the gas flowing out of the gas reformer as a gas temperature (T);
A voltage setting unit that variably sets a search voltage (Vs) applied to the electrode in order to search for a voltage at which discharge from the electrode occurs, and when the application of the voltage to the electrode is started, the search A voltage setting unit (74) for setting the voltage to a predetermined initial voltage (Vbase) ;
When the search voltage is set to increase by the voltage setting unit, a determination value (A) in which an increase amount (ΔT) of the gas temperature with respect to a predetermined increase amount (Vadd) of the search voltage is predetermined. A temperature determination unit (S211, S307) for determining whether or not it is greater than,
An initial stop unit (S216) for stopping application of the initial voltage to the electrode when the temperature determination unit determines that the amount of increase in the gas temperature is greater than the determination value;
Equipped with a,
The voltage setting unit updates the initial voltage to a voltage smaller by a predetermined value when the application of the voltage to the electrode is resumed after the application of the initial voltage is stopped by the initial stop unit.
The said temperature determination part is a discharge control apparatus which determines whether the raise amount of the said gas temperature is larger than the said determination value, when the application of the voltage to the said electrode is started by the said initial voltage . The discharge control device according to any one of claims 1 to 4, wherein the voltage setting unit increases the search voltage in a stepwise manner with a predetermined additional width (Vadd). The discharge control device according to any one of claims 1 to 4, wherein the voltage setting unit continuously increases the search voltage. A pressure acquisition unit (S203, S301) for acquiring the pressure of the gas flowing out of the gas reformer as a gas pressure;
Wherein said gas pressure obtained by the pressure obtaining section, the search voltage and storage execution unit to be stored in the storage unit (61c) in association with the case where the increase amount is greater than the determined value of the gas temperature ( S215, S309),
The discharge control device according to any one of claims 1 to 6 . The gas reformer supplies the reformed gas to an exhaust passage (16) through which exhaust from the internal combustion engine (10) passes.
Claim the exhaust gas pressure is the internal pressure and a application execution unit to start the application of the search voltage to the electrode is smaller than a predetermined reference value (S208, S303) of the exhaust passage 1-7 The discharge control device according to any one of the above. The discharge according to claim 8 , wherein the application execution unit starts applying the search voltage to the electrode, assuming that the exhaust pressure is in a stable state when the internal combustion engine is in an idling state. Control device. A gas reformer (32) that generates ozone by reforming the gas by discharge from the electrode (41);
An ozone passage (31) connected to an internal combustion passage (16) extending from the internal combustion engine (10) and supplying ozone generated by the gas reformer to the internal combustion passage;
A temperature sensor (37a) for detecting the temperature of the gas flowing out of the gas reformer;
A control device (60) for controlling the operation of the gas reformer;
Equipped with a,
The control device includes:
A temperature acquisition unit (S204, S209, S301, S305) for acquiring the temperature of the gas flowing out of the gas reformer as a gas temperature (T);
A voltage setting unit that variably sets a search voltage (Vs) applied to the electrode in order to search for a voltage at which discharge from the electrode occurs, and when the application of the voltage to the electrode is started, the search A voltage setting unit (74) for setting the voltage to a predetermined initial voltage (Vbase);
When the search voltage is set to increase by the voltage setting unit, a determination value (A) in which an increase amount (ΔT) of the gas temperature with respect to a predetermined increase amount (Vadd) of the search voltage is predetermined. A temperature determination unit (S211, S307) for determining whether or not it is greater than,
An initial stop unit (S216) for stopping application of the initial voltage to the electrode when the temperature determination unit determines that the amount of increase in the gas temperature is greater than the determination value;
With
The voltage setting unit updates the initial voltage to a voltage smaller by a predetermined value when the application of the voltage to the electrode is resumed after the application of the initial voltage is stopped by the initial stop unit.
The temperature determination unit is a gas supply device that determines whether or not an increase amount of the gas temperature is larger than the determination value when application of a voltage to the electrode is started at the initial voltage . A discharge control method for controlling the operation of a gas reformer (32) for reforming a gas by discharging from an electrode (41),
The temperature of the gas flowing out from the gas reformer is acquired as the gas temperature (T) (S204, S209, S301, S305),
In order to search for a voltage at which discharge from the electrode occurs, a search voltage (Vs) applied to the electrode is variably set (74),
When starting to apply a voltage to the electrode, the search voltage is set to a predetermined initial voltage (Vbase) (74),
If the search voltage is set to increase, whether or not the gas temperature increase amount (ΔT) with respect to a predetermined increase amount (Vadd) of the search voltage is greater than a predetermined determination value (A). determine (S211, S307),
When it is determined that the amount of increase in the gas temperature is greater than the determination value, the application of the initial voltage to the electrode is stopped (S216),
When the application of the voltage to the electrode is resumed after the application of the initial voltage is stopped, the initial voltage is updated to a voltage smaller by a predetermined value (74),
A discharge control method for determining whether or not an increase in the gas temperature is greater than the determination value when application of a voltage to the electrode is started at the initial voltage (S211, S307) .

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