JP2019163753A - Ozone supply device - Google Patents

Abstract

To provide an ozone supply device which can accurately control an ozone amount by accurately obtaining the ozone amount.SOLUTION: An ozone supply device (30) is provided that is mounted in an exhaust emission control system (1) having a NOx storage reduction type clarification catalyst (21) for eliminating NOx in exhaust emission from an internal combustion engine (10). The ozone supply device (30) comprises: an ozone generator (33) generating ozone from air by electric discharge; a supply-side NOx sensor (25) detecting a NOx amount in gas flowing into the clarification catalyst from the ozone generator; and a control device (40). The control device comprises: a first calculation part (44) acquiring an energy state of the ozone generator at electric discharge, and calculating a generation ratio of the NOx amount and the ozone amount; a second calculation part (45) calculating the generated ozone amount by the ozone generator on the basis of the generation ratio and the NOx amount detected by the supply-side NOx sensor, and a supply-side control part (47) controlling the ozone generator on the basis of the generated ozone amount.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ozone supply device that is mounted on an exhaust purification system that includes a NOx occlusion reduction type purification catalyst that purifies NOx in exhaust gas from an internal combustion engine and that supplies ozone to the purification catalyst.

  In order to remove NOx (nitrogen oxides) contained in the exhaust gas of an internal combustion engine, an exhaust gas purification system that purifies NOx using a NOx occlusion reduction type purification catalyst is known. In the NOx storage reduction purification catalyst, nitrogen dioxide (NO2) has higher storage efficiency than nitrogen monoxide (NO). For this reason, in Patent Document 1, ozone (O3) is supplied by an ozone supply device upstream of the NOx storage reduction purification catalyst, and NO in the exhaust is oxidized to NO2 by the ozone, so that NOx is more efficiently converted. Techniques for occlusion and removal have been proposed.

JP-A-2016-79872

  In an ozone supply device mounted on an exhaust purification system, development of means for detecting the amount of ozone is required in order to control the amount of ozone supplied to a NOx storage reduction type purification catalyst. However, it is currently difficult to directly detect the amount of ozone by sensors that can be mounted on a vehicle or the like.

  In view of the above problems, an object of the present invention is to provide an ozone supply device that can accurately control the amount of ozone by grasping the amount of ozone with high accuracy.

  The present invention provides an ozone supply device that is mounted on an exhaust purification system that includes a NOx storage reduction purification catalyst that purifies NOx in the exhaust gas of an internal combustion engine, and that supplies ozone to the purification catalyst. The ozone supply device includes: an ozone generator that generates ozone from air by discharge; a supply-side NOx sensor that detects an amount of NOx in gas supplied from the ozone generator to the purification catalyst; and the ozone generator. A control device for controlling. The control device acquires an energy state at the time of discharge of the ozone generator, calculates a generation ratio between the NOx amount and the ozone amount from the energy state, the generation ratio, and the supply side NOx. A second calculator that calculates the amount of ozone generated by the ozone generator based on the NOx amount detected by the sensor as a generated ozone amount, and a supply that controls the ozone generator based on the amount of generated ozone A control unit.

  The present inventor has found that when ozone is generated by discharge using air as a raw material, the amount of ozone to be generated and the amount of NOx to be generated have a predetermined generation ratio. Furthermore, the present inventor has found that this generation ratio changes depending on the energy state during discharge of the ozone generator, and has completed the present invention.

  According to the ozone supply device of the present invention, the first calculation unit acquires the energy state at the time of discharge of the ozone generator, and calculates the generation ratio between the NOx amount and the ozone amount based on the energy state. By considering the energy state during discharge of the ozone generator, the generation ratio between the NOx amount and the ozone amount can be calculated more accurately. Further, the second calculation unit calculates the ozone amount generated by the ozone generator as the generated ozone amount based on the generation ratio calculated by the first calculation unit and the NOx amount detected by the supply side NOx sensor. Since the detection value of the supply side NOx amount is applied to the generation ratio calculated with high accuracy by the first calculation unit, the generated ozone amount can be calculated with higher accuracy. In addition, the supply control unit can precisely control the ozone amount supplied from the ozone supply device to the purification catalyst in order to control the ozone generator based on the accurate generated ozone amount calculated by the second calculation unit. it can.

1 is a schematic view of an exhaust purification system including an ozone supply device according to a first embodiment. The schematic diagram of the ozone generator in an ozone supply apparatus. The figure which shows the influence of S / N and discharge current peak value in a discharge energy curve. Explanatory drawing about a discharge current peak value. The figure which shows the influence of the discharge current peak value in the relationship between ozone production amount and NOx production amount. The flowchart of the ozone supply control which ECU performs. Schematic of a combustion system provided with the ozone supply apparatus which concerns on 2nd Embodiment. The figure which shows the influence of S / N and emitted light intensity in a discharge energy curve. The figure which shows the influence of the emitted light intensity in the relationship between ozone production amount and NOx production amount.

(First embodiment)
As shown in FIG. 1, the exhaust purification system 1 is configured as a system that can purify exhaust exhausted from the internal combustion engine 10 with a purification catalyst layer 21. The ozone supply device 30 is mounted on the exhaust purification system 1 in order to supply ozone to the purification catalyst layer 21. The internal combustion engine 10 is a diesel engine, and the air sucked from the intake pipe 11 is compressed by the supercharging device 13 and sucked into the combustion chamber of the internal combustion engine 10, and the fuel injected from the fuel injection valve in the combustion chamber. At the same time, it is used for combustion.

  The supercharger 13 includes an intake air compressor 14 disposed in the intake pipe 11, an exhaust turbine 15 disposed in the exhaust pipe 12, and a rotating shaft 16 that connects the intake compressor 14 and the exhaust turbine 15. When the exhaust turbine 15 is rotated by the exhaust from the internal combustion engine 10, the intake compressor 14 is rotated along with the rotation, and the intake air is supercharged. The intake pipe 11 may be provided with an intercooler as a heat exchanger on the downstream side of the intake compressor 14.

  The intake pipe 11 is provided with an intake air amount sensor 18 that detects the amount of air passing through the intake pipe 11 at a position upstream of the intake air compressor 14. The exhaust pipe 12 is provided with an exhaust temperature sensor 22 for detecting the exhaust temperature, an exhaust pressure sensor 23 for detecting the exhaust pressure, and an exhaust side NOx sensor 24 for detecting the NOx amount generated in the engine as a concentration. A purification catalyst layer 21 is provided on the downstream side of the exhaust temperature sensor 22, the exhaust pressure sensor 23, and the exhaust side NOx sensor 24.

  The purification catalyst layer 21 includes a NOx storage reduction type catalyst. As is well known, the purification catalyst layer 21 occludes NOx contained in the exhaust during lean combustion, and occluded using reducing components such as HC and CO contained in the exhaust during post injection, for example. NOx is reduced and removed. The purification catalyst layer 21 has, for example, a structure in which silver as a reduction catalyst is supported on alumina coated on the support surface. Exhaust gas from the internal combustion engine 10 passes through the exhaust pipe 12 and is purified in the purification catalyst layer 21.

  The ozone supply device 30 includes an air pump 32 and an ozone generator 33. The air pump 32 is, for example, an electric pump, and can pressurize air sucked from outside and blow it to the ozone generator 33. An air amount sensor 35 is provided at the outlet of the air pump 32, and the flow rate of air blown from the air pump 32 to the ozone generator 33 can be detected.

  The ozone generator 33 is connected via an ozone supply pipe 31. The ozone supply pipe 31 is connected to the exhaust pipe 12 at a position upstream of the purification catalyst layer 21 and downstream of the exhaust temperature sensor 22, exhaust pressure sensor 23, and exhaust side NOx sensor 24. The ozone supply pipe 31 is provided with an on-off valve 34 for the purpose of suppressing the backflow of the exhaust gas from the exhaust pipe 12. The on-off valve 34 is opened when ozone is supplied to the exhaust pipe 12, and is closed when ozone supply is stopped. The ozone supply pipe 31 is provided with a supply-side NOx sensor 25 that detects the NOx amount as a concentration at a position between the ozone generator 33 and the on-off valve 34. The supply-side NOx sensor 25 can detect the amount of NOx in the gas supplied from the ozone generator 33 to the purification catalyst layer 21.

  As shown in FIG. 2, the ozone generator 33 includes a housing 36, a plurality of electrode plates 37 disposed in the housing 36, and a transformer 39 that controls a voltage applied to the electrode plates 37. Air supplied from the air pump 32 passes through the housing 36. The plurality of electrode plates 37 are arranged at predetermined intervals in a direction substantially orthogonal to the air flow direction, and the air passes through the plurality of flow paths 38 separated by the plurality of electrode plates 37. When a high voltage is applied between the plurality of electrode plates 37 by the transformer 39 and discharge occurs, ozone is generated from the air flowing through the flow path 38.

  Ozone (O 3) generated by the ozone generator 33 is supplied to the upstream side of the purification catalyst layer 21 in the exhaust pipe 12 through the ozone supply pipe 31. By supplying ozone, NO in the exhaust gas flowing into the purification catalyst layer 21 from the exhaust pipe 12 can be oxidized to NO 2, thereby increasing the NOx storage capacity in the purification catalyst layer 21. In particular, when the temperature of the purification catalyst layer 21 is low, the NO storage efficiency is lowered. Therefore, it is preferable to supply ozone to the purification catalyst layer 21 to oxidize NO to NO2 in order to ensure the storage efficiency.

  When ozone is supplied to the exhaust pipe 12 during operation of the internal combustion engine 10, voltage is applied by the transformer 39 in the ozone generator 33 to generate ozone. In a state where ozone is generated, the air pump 32 is driven and the on-off valve 34 is opened, so that ozone flows into the exhaust pipe 12 together with the air passing through the ozone generator 33. Further, NO and NO 2 are occluded in the purification catalyst layer 21 and reduced and purified while an oxidation reaction from NO to NO 2 is performed by ozone on the upstream side of the purification catalyst layer 21.

  The detected values of the intake air amount sensor 18, the exhaust temperature sensor 22, the exhaust pressure sensor 23, the exhaust side NOx sensor 24, the supply side NOx sensor 25, and the air amount sensor 35 are output to the ECU 40. The ECU 40 is an electronic control unit mainly composed of a microcomputer including a CPU, a ROM, a RAM, and the like. The ECU 40 executes various control programs stored in the ROM, and based on the detection signals of the various sensors described above. Various controls of the internal combustion engine 10 and the exhaust purification system 1 are executed. The ECU 40 has a function of executing combustion control of the internal combustion engine 10 and also has a function of a control device that executes control of an ozone supply amount from the ozone supply device 30.

  The ECU 40 includes a data acquisition unit 41, a storage unit 42, a calculation unit 43, and a supply control unit 47. The data acquisition unit 41 acquires detection values of various sensors such as detection values of the intake air amount sensor 18, the exhaust temperature sensor 22, the exhaust pressure sensor 23, the exhaust side NOx sensor 24, the supply side NOx sensor 25, and the air amount sensor 35. . The data acquired by the data acquisition unit 41 may be stored in the ECU 40 by the storage unit 42.

  The calculation unit 43 includes a first calculation unit 44, a second calculation unit 45, and a third calculation unit 46. The first calculation unit 44 acquires an energy state during discharge of the ozone generator 33 (hereinafter referred to as a discharge energy state), and a generation ratio (hereinafter referred to as O / N) of the NOx amount and the ozone amount from the discharge energy state. (Sometimes referred to as a generation ratio).

In the ozone generator 33, when ozone is generated by discharge using air as a raw material, as shown in the following formulas (1) and (2), oxygen radicals (O.O.) are converted from oxygen molecules (O2) in the air by discharge. ) Is generated, and ozone is generated from oxygen radicals and oxygen molecules. However, since nitrogen molecules (N2) are also contained in the air, as shown in the following formulas (3) and (4), NOx is formed as a by-product by the reaction between oxygen radicals and nitrogen molecules. Can be generated as
O2 + e → 2O ... (1)
O2 + O · → O3 (2)
N2 + O · → NO + N · (3)
N ・ + O ・ → NO (4)

As a result of diligent research, the present inventor has found that the amount of ozone generated in the ozone generator 33 is correlated with the amount of NOx. The reaction rate formula of the oxygen radical generation reaction shown in the above formula (1) can be expressed by the following formula (5). [O ·] is the oxygen radical concentration, [O2] is the oxygen concentration, ke is the rate coefficient, and ne is the electron density. D [O ·] / dt indicates the generation rate of oxygen radicals, and the product of ke and ne is a plasma parameter.
d [O ·] / dt = ke × ne × [O2] (5)

  In the ozone generation reaction in which ozone is generated from air by discharge, the O / N generation ratio varies depending on the discharge energy state in the ozone generator 33. As an example of the discharge energy state, an energy distribution of electrons during discharge in the ozone generator 33 can be given. When the energy of electrons is in a predetermined range, ozone that is a main product can be generated with high efficiency. This predetermined energy region is referred to as an ozone generation region. The ozone generation region can be defined by an upper limit value X1 and a lower limit value X2. The more electrons having an energy value X that satisfy X1 ≦ X ≦ X2, the greater the ratio of ozone amount.

  The energy distribution of electrons can be obtained by calculating an electron energy distribution function (EEDF) shown in FIG. The EEDF can be calculated by a known method based on the Boltzmann equation.

  In FIG. 3, the change of EEDF by conversion electric field strength S / N is shown. S / N is electric field strength: S divided by molecular number density: N. The curves L1 to L5 are in the order of L1, L2, L3, L4 and L5 from the smaller S / N to the larger S / N. The larger the S / N, the more the maximum value of EEDF shifts to the higher energy side.

  FIG. 3 shows an ozone generation region where the range of electron energy values is X1 ≦ X ≦ X2. The region where the electron energy value X <X1 is a low decomposition region, and both ozone and NOx are hardly generated. Further, the region where the electron energy value is X ≧ X2 is the NOx generation region, and the NOx generation ratio increases and the ozone generation efficiency decreases. The generation ratio of ozone and NOx in the ozone generation region is about O3: NOx = 100: 1, and the generation ratio of ozone and NOx in the NOx generation region is about O3: NOx = 10: 1. In order to increase the amount of ozone generated, for example, as indicated by L3, it is preferable to control the ozone generator 33 so that the EEDF has many electrons having energy values X belonging to the ozone generation region.

  The converted electric field strength S / N varies depending on the energy intensity of the discharge energy that is energy supplied at the time of discharge. The intensity of the discharge energy is calculated from a detection value or an input value for a predetermined physical quantity such as a discharge current flowing between the electrode plates 37 of the ozone generator 33, an applied voltage applied to the electrode plate 37, and a light emission intensity at the time of discharge. be able to. The EEDF changes as the physical quantity that changes the converted electric field strength S / N changes. The EEDF also changes depending on the temperature or humidity of the air supplied from the air pump 32 to the ozone generator 33. A predetermined physical quantity for changing the EEDF at the time of discharge of the ozone generator 33 (for example, the intensity of discharge energy exemplified above, the discharge current flowing between the electrode plates 37, the applied voltage applied to the electrode plate 37, the light emission at the time of discharge) The intensity and the temperature or humidity of the air supplied to the ozone generator 33 can be used as parameters that affect the electron energy distribution (hereinafter referred to as influence parameters). The influence parameter is an example of a parameter indicating a discharge energy state of the ozone generator 33.

  For example, FIG. 4 shows the change over time of the discharge current flowing between the electrode plates 37 during discharge. 4 correspond to the EEDFs indicated by L1 to L5 in FIG. 3, respectively. That is, the converted electric field strength S / N increases as the maximum value of the discharge current value increases. Note that the value of the discharge current may be a value obtained by detecting a current flowing during discharge with an ammeter or the like, or may be a value calculated from an applied voltage applied to the transformer 39.

  The 1st calculation part 44 acquires an influence parameter as a discharge energy state of the ozone generator 33, for example. The influence parameter is a parameter that affects the EEDF and the O / N generation ratio. Further, EEDF is calculated based on the influence parameter. Then, from the calculated EEDF, the ratio of electrons having energy values belonging to the ozone generation region as shown in FIG. 3 and the ratio of electrons having energy values belonging to the NOx generation region as shown in FIG. The generation ratio can be calculated. According to the first calculation unit 44, the influence parameter is acquired in consideration of the change of the discharge energy state depending on the discharge condition or the like in the ozone generator 33, and the O / N generation ratio is accurately calculated based on the influence parameter. it can.

  FIG. 5 shows the O / N generation ratio calculated by obtaining the peak value (maximum value) of the discharge current shown in FIG. 4 as an influence parameter. As shown in L3, when an EEDF having many electrons having an energy value X belonging to the ozone generation region is obtained, the slope in FIG. 5 increases, and the ratio of the ozone amount to the NOx amount increases. Instead of the peak value of the discharge current, a time integration value obtained by integrating the discharge current with time may be used as the influence parameter.

  The ECU 40 may store in advance an O / N generation ratio as shown in FIG. That is, the calculation unit 43 may calculate the O / N generation ratio by applying the acquired influence parameter to a mathematical formula or a map stored in the ECU 40. Alternatively, the first calculation unit 44 may be configured to calculate an O / N generation ratio during operation of the ozone supply device. Alternatively, the first calculation unit 44 calculates the O / N generation ratio during operation of the ozone supply device 30 and corrects the mathematical formula and the map stored in the ECU 40 based on the calculated O / N generation ratio. It may be configured.

  The second calculation unit 45 generates the ozone amount generated by the ozone generator 33 based on the O / N generation ratio calculated by the first calculation unit 44 and the NOx amount detected by the supply side NOx sensor 25. Calculate as a quantity. According to the second calculation unit 45, the generated ozone is more accurately generated by using the O / N generation ratio calculated with high accuracy by the first calculation unit 44 and using the NOx amount detected by the supply side NOx sensor 25. The amount can be calculated.

  The third calculator 46 calculates the amount of ozone required for the purification catalyst layer 21 to purify NOx in the exhaust gas of the internal combustion engine 10 as the required ozone amount based on the NOx amount detected by the exhaust side NOx sensor 24. The third calculator 46 can calculate the required ozone amount based on the NOx amount detected by the exhaust-side NOx sensor 24, the exhaust temperature of the internal combustion engine 10, and the exhaust flow rate. The exhaust temperature and the exhaust flow rate of the internal combustion engine 10 can be calculated from the detected values of the intake air amount sensor 18 and the exhaust temperature sensor 22, respectively.

  The supply control unit 47 operates the ozone supply device 30 in accordance with the operation state of the internal combustion engine 10 and executes ozone supply to the purification catalyst layer 21. For example, when a request for ozone supply occurs during lean combustion of the internal combustion engine 10, the ozone supply device 30 is operated to supply ozone to the exhaust pipe 12.

  During operation of the ozone supply device 30, the supply control unit 47 controls the ozone generator 33 based on the amount of generated ozone calculated by the second calculation unit 45, and controls the amount of ozone supplied by the ozone supply device 30. In order to control the amount of ozone, the supply control unit 47 may also control the air pump 32 and the on-off valve 34. The supply control unit 47 can control the ozone supply device 30 based on the generated ozone amount that is accurately calculated by the second calculation unit 45 in consideration of the discharge condition of the ozone generator 33 and the like. As a result, the ozone supply amount can be appropriately controlled, and consequently, the NOx purification in the purification catalyst layer 21 can be properly realized.

  The supply control unit 47 feeds back the ozone supply device 30 so that the amount of generated ozone calculated by the second calculation unit 45 approaches the amount of ozone required by the purification catalyst layer 21 (hereinafter referred to as the necessary amount of ozone). It may be configured to control. Specifically, the ozone generator may be controlled such that the difference between the required ozone amount and the generated ozone amount is a predetermined threshold value or less.

  For example, when the difference between the required ozone amount and the generated ozone amount is a predetermined threshold value or less, the ozone supply is continued under the same condition, and when the difference between the required ozone amount and the generated ozone amount exceeds the predetermined threshold value, The control conditions of the ozone supply device 30 may be corrected. Regarding the correction of the control condition, when the required ozone amount is larger than the generated ozone amount, the generated ozone amount is increased. When the required ozone amount is smaller than the generated ozone amount, the generated ozone amount is decreased. Can be. The amount of generated ozone can be increased by increasing the output of the ozone generator 33, for example.

  FIG. 6 is a flowchart showing a supply control process in the ozone supply device 30, and this process is repeatedly performed by the ECU 40 at a predetermined cycle.

  In steps S10 to S12, data relating to the operating state of the internal combustion engine 10 is acquired or calculated. First, in step S10, the detection values of the intake air amount sensor 18, the exhaust gas temperature sensor 22, and the exhaust side NOx sensor 24 and the fuel injection amount injected into the internal combustion engine 10 are acquired as the exhaust side data. Next, in step S11, the exhaust flow rate of the internal combustion engine 10 is calculated based on the detected value of the intake air amount sensor 18 and the fuel injection amount. Next, in step S12, the NOx amount in the exhaust gas is calculated based on the exhaust gas flow rate calculated in step S11 and the detected value of the exhaust side NOx sensor 24 acquired in step S10. After step S12, the process proceeds to step S13.

  In steps S13 and S14, data relating to the purification catalyst layer 21 installed in the exhaust pipe 12 of the internal combustion engine 10 is acquired or calculated. First, in step S13, the temperature of the purification catalyst layer 21 is calculated from the exhaust gas flow rate of the internal combustion engine 10 calculated in step S11 and the exhaust gas temperature acquired in step S10. Next, in step S14, the exhaust gas temperature acquired in step S10, the exhaust gas flow rate calculated in step S11, the NOx amount in the exhaust gas calculated in step S12, and the temperature of the purification catalyst layer 21 calculated in step S13. Based on this, the required ozone amount Y1 is calculated. After step S14, the process proceeds to step S15.

  In step S15, based on the required ozone amount calculated in step S14, the target air amount sucked by the air pump 32 and the target voltage applied by the transformer in the ozone generator 33 are calculated. Further, the target air amount and the target voltage are output as control values to the ozone supply device 30, and an instruction is given to generate ozone based on the target air amount and the target voltage. After step S15, the process proceeds to step S16.

  In steps S16 to S20, the amount of ozone generated by the ozone generator 33 is calculated. First, in step S16, the detection value of the supply side NOx sensor 25 is acquired as the ozone supply side data.

  Next, in step S17, the NOx amount generated by the ozone generator 33 is calculated based on the target air amount calculated in step S15 and the detected value of the supply side NOx sensor 25.

  Next, in step S18, an influence parameter is acquired. Acquisition of the influence parameter in step S18 corresponds to acquiring the discharge energy state of the ozone generator 33. In this embodiment, the peak value of the discharge current when the target voltage is applied to the ozone generator 33 is acquired as the influence parameter. The discharge current may be calculated based on the target voltage, or may be a current detected when discharging is performed by applying the target voltage.

  Next, in step S19, the O / N generation ratio in the ozone supply pipe 31 is calculated based on the peak value of the discharge current acquired in step S18. The ECU 40 stores a mathematical expression or a map showing the relationship between the peak value of the discharge current and the O / N generation ratio as shown in FIG. 5, and based on the peak value of the discharge current, the O / N generation ratio is stored. Can be calculated.

  Next, in step S20, based on the O / N generation ratio calculated in step S19, the ozone amount (generated ozone amount Y2) supplied from the ozone supply device 30 to the exhaust pipe 12 from the NOx amount calculated in step S17. ) Is calculated.

  Next, in step S21, it is determined whether or not | Y1-Y2 |, which is the absolute value of the difference obtained by subtracting the generated ozone amount Y2 from the required ozone amount Y1, exceeds a predetermined threshold value. In step S21, when | Y1-Y2 | is equal to or less than the threshold value, the process is terminated, and the operation is continued without changing the control value in the ozone supply device 30. That is, the control of the ozone supply device 30 is continued using the target air amount and the target voltage as control values. If | Y1-Y2 | exceeds the threshold value in step S21, the process proceeds to step S22.

  In step S22, the sign of Y1-Y2, which is the difference between the required ozone amount Y1 and the generated ozone amount Y2, is determined. When Y1-Y2 is a positive value, the process proceeds to step S23, the output of the ozone generator 33 is increased, and the process is terminated. When the generated ozone amount Y2 is insufficient with respect to the required ozone amount Y1, the generated ozone amount can be increased by increasing the output of the ozone generator 33 or the like. In step S22, when Y1-Y2 is a negative value, the process proceeds to step S24, and the output of the ozone generator 33 is decreased. When the generated ozone amount Y2 is excessive with respect to the required ozone amount Y1, the generated ozone amount can be reduced by reducing the output of the ozone generator 33 or the like.

(Second Embodiment)
The second embodiment will be described focusing on the differences from the first embodiment. In the second embodiment, a case where the light emission intensity during discharge is used as an influence parameter instead of the discharge current will be described as an example. As shown in FIG. 7, in the ozone supply device 50 according to the second embodiment, the ozone generator 33 is provided with a light intensity sensor 27 that measures the emission intensity at the time of discharge. The detection value of the light intensity sensor 27 is output to the ECU 40. The other configuration is the same as that of the exhaust purification system 1 shown in FIG.

  FIG. 8 shows the converted electric field intensity S / N and the change according to the emission intensity detected by the photometric sensor 27, and the change of the EEDF accompanying it. As the emission intensity increases, the converted electric field strength S / N increases, and the maximum value of the EEDF shifts to a higher energy side. The curves L6 to L10 are in the order of L6, L7, L8, L9, and L10 from the smaller S / N to the larger S / N.

  The calculation unit 43 can calculate EEDF as the influence parameter based on the emission intensity detected by the light intensity sensor 27. Further, the calculation unit 43 calculates, from the calculated EEDF, the proportion of electrons having an energy value belonging to the ozone generation region as shown in FIG. 8 and the proportion of electrons having an energy value belonging to the NOx generation region. Thereby, the O / N generation ratio as shown in FIG. 9 can be calculated.

  Also in the second embodiment, the processing supply control process similar to that in FIG. 6 is performed, the generated ozone amount is calculated, and the control of the ozone supply device 30 can be executed using this generated ozone amount. In the second embodiment, in step S18, the emission intensity detected by the light intensity sensor 27 is acquired as the influence parameter. In step S19, an O / N generation ratio is calculated based on the light emission intensity acquired in step S18. The ECU 40 stores a mathematical expression or a map showing the relationship between the light emission intensity and the O / N generation ratio as shown in FIG. 8, and can calculate the O / N generation ratio based on the light emission intensity. .

  According to said embodiment, the following outstanding effects are acquired.

  The first calculation unit 44 acquires a predetermined physical quantity (such as a discharge current value) that affects the electron energy distribution of the discharge of the ozone generator 33 as the discharge energy state of the ozone generator 33 that changes the O / N generation ratio. The O / N generation ratio is calculated based on the acquired predetermined physical quantity. The second calculation unit 45 calculates the generated ozone amount based on the O / N generation ratio accurately calculated by the first calculation unit 44 and the NOx amount detected by the supply side NOx sensor 25. By using the influence parameter, the O / N generation ratio can be obtained with higher accuracy, and therefore the accuracy when the generated ozone amount is calculated based on the detected value of the NOx amount in the ozone supply pipe 31 becomes higher. Since the supply control unit 47 controls the ozone supply device 30 based on the highly accurate generated ozone amount calculated by the second calculation unit 45, the supply control unit 47 precisely controls the ozone amount supplied from the ozone supply device 30 to the purification catalyst layer 21. Can be controlled.

  Further, the supply control unit 47 feedback-controls the ozone supply device 30 so that the generated ozone amount calculated by the second calculation unit 45 approaches the required ozone amount of the third calculation unit 46. For this reason, the ozone supply amount can be appropriately controlled, and consequently, the NOx purification in the purification catalyst layer 21 can be appropriately realized.

DESCRIPTION OF SYMBOLS 1 ... Exhaust purification system, 10 ... Internal combustion engine, 21 ... Purification catalyst layer, 25 ... Supply side NOx sensor, 30 ... Ozone supply device, 33 ... Ozone generator, 40 ... Control device, 44 ... 1st calculation part, 45 ... 2nd calculation part, 47 ... supply control part

Claims (6)

An ozone supply device (30) that is mounted in an exhaust purification system (1) having a NOx occlusion reduction purification catalyst (21) that purifies NOx in the exhaust gas of the internal combustion engine (10) and supplies ozone to the purification catalyst. Because
An ozone generator (33) for generating ozone from the air by discharge;
A supply side NOx sensor (25) for detecting the amount of NOx in the gas supplied from the ozone generator to the purification catalyst;
A control device (40) for controlling the ozone generator,
The controller is
A first calculation unit (44) that acquires an energy state during discharge of the ozone generator, and calculates a generation ratio of the NOx amount and the ozone amount from the energy state;
A second calculation unit (45) that calculates an ozone amount generated by the ozone generator as a generated ozone amount based on the generation ratio and the NOx amount detected by the supply-side NOx sensor;
An ozone supply device comprising: a supply control unit (47) for controlling the ozone generator based on the generated ozone amount.   The ozone supply device according to claim 1, wherein the energy state is a predetermined physical quantity that affects an electron energy distribution during discharge of the ozone generator.   The predetermined physical quantity includes energy intensity at the time of discharge of the ozone generator, light emission intensity at the time of discharge, applied voltage at the time of discharge, discharge current at the time of discharge, temperature of air supplied to the ozone generator, or The ozone supply device according to claim 2, wherein the ozone supply device is at least one of humidity.   The ozone supply device according to claim 2 or 3, wherein the predetermined physical quantity is at least one of a peak value and a time integral value of a discharge current of the ozone generator. The exhaust purification system further includes an exhaust side NOx sensor (24) for detecting the amount of NOx in the exhaust from the internal combustion engine,
The control device calculates, based on the NOx amount detected by the exhaust side NOx sensor, the amount of ozone required for the purification catalyst to purify NOx in the exhaust gas of the internal combustion engine as a required ozone amount. (46)
The ozone supply device according to any one of claims 1 to 4, wherein the supply control unit controls the ozone generator so that a difference between the required ozone amount and the generated ozone amount is a predetermined threshold value or less.   The ozone supply device according to claim 5, wherein the third calculation unit calculates the required ozone amount based on the NOx amount detected by the exhaust-side NOx sensor, the exhaust temperature and the exhaust flow rate of the internal combustion engine.

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