JP2006112383A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely coagulate and collect an exhaust particulate (PM), by generating efficient corona discharge, in an exhaust particulate (PM) purifying device using the corona discharge. <P>SOLUTION: This exhaust emission control device has a discharge electrode 3, a conductive net 2 and a high voltage power source 4; and is characterized in that a temperature sensor 5 for detecting the exhaust gas temperature is arranged in a housing 1, and a voltmeter 6 and an ammeter 7 are arranged between the discharge electrode 3 and the high voltage power source 4, and an electronic control unit ECU is arranged for performing ON/OFF control of a switch of the high voltage source 4 and control of an impression voltage value or an arc discharge generation predicting voltage value on the basis of data from the temperature sensor 5 and the ammeter 7 and data on an engine speed and a fuel injection quantity from an internal combustion engine system. Thus, the efficient corona discharge can be generated in response to a temperature change in exhaust gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine that collects, collects and collects exhaust particulate (PM) contained in exhaust gas of the internal combustion engine by corona discharge.

  Treatment of fine particles contained in the exhaust gas of an internal combustion engine has become a major issue. As a prior art, there is Patent Document 1, in which a round bar electrode is disposed in an exhaust pipe as a discharge electrode, and a high voltage is applied between the discharge electrode and the collection electrode using a peripheral portion of the exhaust pipe and a metal honeycomb as a collection electrode. By generating corona discharge, negative ions are charged to the exhaust particulates (PM) discharged from the diesel engine, and the charged exhaust particulates (PM) are attracted to the periphery of the exhaust pipe as a collecting electrode or to the metal honeycomb by Coulomb force. And adsorbed technology is presented.

  However, the exhaust emission control device simply installs a discharge electrode, uses a portion around the exhaust pipe and a metal honeycomb as a collector electrode, applies a high voltage between the discharge electrode and the collector electrode, generates corona discharge, and generates exhaust particulate (PM). Only the general configuration of charging negative ions is presented, and no consideration is given to the relationship between the exhaust gas temperature changing from room temperature to high temperature and the applied voltage. For this reason, for example, in the above-described configuration, when the exhaust gas temperature is low and condensation occurs on the electrode, the voltage is continuously applied even if the current is applied and leaks and no corona discharge occurs. On the other hand, arc discharge frequently occurs, the exhaust particulates (PM) are not efficiently charged, and as a result, the exhaust particulates (PM) cannot be efficiently aggregated and collected. There is a problem.

JP 2002-147218 A

  The present invention is intended to improve the above-mentioned drawbacks of the prior art, and in particular, by analyzing the relationship between the change in exhaust gas temperature changing from room temperature level to high temperature and the appropriate applied voltage. Effectively applying the correlation, determining whether to turn on or off the voltage power switch according to the exhaust gas temperature, and further setting the applied voltage value or the predicted arc discharge voltage value according to changes in the exhaust gas temperature, so that it is always efficient It is intended to realize the generation of corona discharge. As a result, exhaust particulates (PM) are efficiently charged, enabling efficient aggregation or collection of exhaust particulates (PM) using corona discharge, realizing a high-performance exhaust purification system for internal combustion engines. can do.

  In the exhaust gas purification apparatus for an internal combustion engine according to claim 1, a high voltage is applied between the electrodes in the exhaust part of the internal combustion engine to generate corona discharge to charge the exhaust particulates and to aggregate the charged exhaust particulates. The exhaust gas purifying device for an internal combustion engine to be collected has an exhaust gas temperature detecting means and a high voltage power supply, and has a control means for controlling the switch of the high voltage power supply to ON or OFF based on the detected exhaust gas temperature. It is a feature.

Since the exhaust purification apparatus has such a configuration, the high-pressure power switch is always set only in the exhaust gas temperature range to which voltage should be applied by measuring the exhaust gas temperature during operation and checking the detected exhaust gas temperature. Since the switch can be controlled to be turned off under conditions other than the above, there is an effect that unnecessary voltage application is not required.

  Preferably, the control means turns off the high-voltage power switch when the detected exhaust gas temperature is lower than the dew condensation temperature of the electrode portion, and turns on the high-voltage power switch when the temperature is high. Control to

  With this configuration, for example, if dew condensation occurs on the electrode, it will leak even if it is energized and corona discharge will not occur.Therefore, by setting the dew generation temperature in advance, if the detected exhaust gas temperature is lower than the dew generation temperature, the switch Can be controlled so that the switch is turned on when the detected exhaust gas temperature exceeds that temperature.

  As in the invention of claim 3, the dew condensation temperature is set to 50 to 70 ° C.

  From experience, the upper limit temperature for the occurrence of condensation in the electrode is most often in the range of 50 to 70 ° C. By configuring in this way, when the detected exhaust gas temperature is below the condensation occurrence temperature, the switch is turned off, When the detected exhaust gas temperature exceeds that temperature, control can be performed to turn on the switch.

  According to a fourth aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine, wherein a high voltage is applied between electrodes in an exhaust portion of the internal combustion engine to generate corona discharge to charge exhaust particulates and to aggregate the charged exhaust particulates. An exhaust gas purification apparatus for an internal combustion engine that collects is characterized in that an exhaust gas temperature detection means and a voltage variable high voltage power supply are provided, and a control means for controlling an applied voltage value based on the detected exhaust gas temperature is provided. Is.

  In general, if the applied voltage is high, more ions can be generated, so the voltage should be set as high as possible. However, if the applied voltage is too high, arc discharge will be generated and corona discharge will be stopped to achieve the expected performance. Can not be. In addition, the higher the exhaust gas temperature, the lower the arc discharge generation voltage, and the relationship between the temperature change and the arc discharge generation voltage greatly affects the efficient corona discharge generation. Since the present invention is configured as described above, it has an effect that an appropriate voltage corresponding to the situation can be applied by always detecting the temperature of the exhaust gas.

  As in the fifth aspect of the invention, the applied voltage value is set to be equal to or less than the arc discharge predicted voltage value.

  With this configuration, it is possible to always select the best applied voltage value corresponding to the exhaust gas temperature at that time, while avoiding a voltage region that may cause arc discharge. For this reason, efficient corona discharge can always be generated, and as a result, exhaust particulates (PM) can be aggregated and collected efficiently.

  As in the sixth aspect of the present invention, the expected arc discharge occurrence voltage value is calculated from the amount of exhaust particulate (PM) determined by the detected exhaust gas temperature and the internal combustion engine operating conditions.

  In general, the arc discharge generation voltage varies depending on the temperature of the exhaust gas and the amount of exhaust particulates (PM). With this configuration, the applied voltage value and the expected arc discharge generation voltage value at each time point are more accurate. Can be calculated.

  As in the seventh aspect of the invention, the items of the internal combustion engine operating condition are the internal combustion engine speed and the fuel injection amount.

  With this configuration, it is possible to reliably calculate the change in the generation amount of exhaust particulates (PM), and as a result, it is possible to accurately calculate the above-mentioned expected arc discharge occurrence voltage value.

  The exhaust emission control device for an internal combustion engine according to claim 8 is configured to charge corona discharge by applying a high voltage between the electrodes in the exhaust part of the internal combustion engine to charge the exhaust particulates and aggregate the charged exhaust particulates. An exhaust gas purifying device for an internal combustion engine to be collected includes an exhaust gas temperature detecting means and a voltage variable high voltage power source, and controls the voltage variable high voltage power source to ON or OFF based on the detected exhaust gas temperature, and based on the detected exhaust gas temperature. Control means for controlling the applied voltage value is provided.

  In the above exhaust purification device, always measure the exhaust gas temperature during operation and check the detected exhaust gas temperature to turn on the voltage variable high-voltage power switch only in the exhaust gas temperature range where the voltage should be applied. Then, since the switch can be controlled to be turned off, there is an effect that unnecessary application is not required. In general, if the applied voltage is high, more ions can be generated. Therefore, the voltage should be set as high as possible. However, if the voltage is too high, arc discharge is generated and corona discharge is stopped, and the expected performance is exhibited. Can not do. On the other hand, the higher the exhaust gas temperature, the lower the arc discharge generation voltage, and the relationship between the temperature change and the arc discharge generation voltage greatly affects the efficient corona discharge generation. Since the present invention is configured as described above, by always detecting the temperature of the exhaust gas, in addition to the ON / OFF control of the power switch, the appropriate applied voltage value is controlled according to the situation. It has the effect that it can be performed.

  As in the ninth aspect of the invention, the control means turns off the voltage variable high voltage power supply when the detected exhaust gas temperature is lower than the dew condensation temperature of the electrode portion, and turns on the voltage variable high voltage power supply when it is higher. It is characterized by controlling to.

With this configuration, for example, if dew condensation occurs on the electrode, it will leak even if it is energized, and no corona discharge will occur. When the detected exhaust gas temperature exceeds that temperature, the switch can be turned on.

  As in the invention of claim 10, the upper limit temperature of condensation is 50 to 70 ° C.

  According to experience, the upper limit temperature of occurrence of dew condensation in the electrode is most frequently in the range of 50 to 70 ° C., and thus the detected exhaust gas temperature is surely set to the dew condensation occurrence temperature. In the following, the control can be performed so that the switch is turned off and the switch is turned on when the detected exhaust gas temperature exceeds that temperature.

  As in the eleventh aspect of the invention, the applied voltage value is set to be equal to or lower than the expected arc discharge occurrence voltage value.

  With this configuration, it is possible to always select the best applied voltage value corresponding to the exhaust gas temperature at that time, while avoiding a voltage region that may cause arc discharge. For this reason, efficient corona discharge can always be generated, and as a result, exhaust particulates (PM) can be aggregated and collected efficiently.

  As in the twelfth aspect of the present invention, the expected arc discharge occurrence voltage value is calculated from the detected exhaust gas temperature and the amount of exhaust particulate (PM) determined by the internal combustion engine operating conditions.

Since the arc discharge generation voltage varies depending on the temperature of the exhaust gas and the amount of exhaust particulates (PM), by configuring in this way, the expected arc discharge generation voltage value at each time point can be calculated more accurately.

As in the thirteenth aspect of the invention, the items of the internal combustion engine operating condition are the internal combustion engine speed and the fuel injection amount.

  With this configuration, it is possible to reliably calculate the change in the generation amount of exhaust particulates (PM), and as a result, it is possible to accurately calculate the above-mentioned expected arc discharge occurrence voltage value.

  The exhaust emission control device for an internal combustion engine according to claim 14 is configured such that a high voltage is applied between the electrodes to generate corona discharge in the exhaust portion of the internal combustion engine to charge the exhaust particulates, and the charged exhaust particulates are aggregated. An exhaust gas purifying device for an internal combustion engine to be collected includes exhaust gas temperature detection means, current detection means and voltage variable high voltage power supply, and controls voltage variable high voltage power supply to ON or OFF based on detected exhaust gas temperature to detect exhaust gas Control means is provided for controlling the applied voltage value based on the temperature and controlling the applied voltage value to drop to the arc discharge non-generated voltage value based on arc discharge detection by the current detecting means.

  In the above exhaust purification device, always measure the exhaust gas temperature during operation and check the detected exhaust gas temperature to turn on the voltage variable high-voltage power switch only in the exhaust gas temperature range where the voltage should be applied. Then, since it can be controlled to turn off the switch, there is an effect that unnecessary voltage application is not required. In general, if the applied voltage is high, more ions can be generated. Therefore, the voltage should be set as high as possible. However, if the voltage is too high, arc discharge is generated and corona discharge is stopped, and the expected performance is exhibited. Can not do. On the other hand, the higher the exhaust gas temperature, the lower the arc discharge generation voltage, and the relationship between the temperature change and the arc discharge generation voltage greatly affects the efficient corona discharge generation. Since the present invention is configured as described above, by always detecting the temperature of the exhaust gas, in addition to the ON / OFF control of the voltage variable high-voltage power switch, an appropriate applied voltage value according to the situation is set. Control is possible and the arc discharge occurrence expected voltage value is different from the actual arc discharge occurrence voltage value and the applied voltage value is lower than the expected arc discharge occurrence voltage value. When this occurs, the applied voltage value can be automatically controlled to drop to the arc discharge non-generated voltage value.

  The exhaust emission control device for an internal combustion engine according to claim 15 includes exhaust gas humidity detection means instead of the exhaust gas temperature detection means, and the control means turns on or off the high-voltage power supply based on the detected exhaust gas humidity. It is characterized by controlling.

With this configuration, the present invention detects the humidity of the exhaust gas during operation by using the exhaust gas humidity detection means instead of the exhaust gas temperature detection means. With respect to the expected humidity range, the high-voltage power switch is turned off, and the switch can be turned on except under the conditions, so that it is possible to avoid unnecessary application.

  As described above, according to the above configuration, the high-pressure power switch is turned on only in the range of the exhaust gas temperature to which the voltage should be applied by always measuring the exhaust gas temperature during operation and checking the detected exhaust gas temperature. In other conditions, the switch is turned off, and an appropriate applied voltage value can be set based on changes in exhaust gas temperature. If an arc discharge occurs unexpectedly, it is automatically applied. Since the voltage value is controlled to be lowered to the voltage value at which arc discharge is not generated, it can be controlled to generate corona discharge extremely efficiently. Therefore, as a result, a practical exhaust purification device for an internal combustion engine that can aggregate and collect exhaust particulates (PM) extremely efficiently can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an internal combustion engine system. The exhaust purification apparatus of the present invention is connected to the exhaust pipe from the internal combustion engine (engine), and further a DPF (Diesel Particulate Filter) is connected. It is what you are doing.

  FIG. 2 shows an embodiment of the present invention, which is an enlarged view of the exhaust purification device shown in FIG. Reference numeral 1 denotes an exhaust purification device housing which is made of stainless steel (SUS) and is electrically installed. Although not shown, the left end portion of the housing 1 is connected to the internal combustion engine via an exhaust pipe, and exhaust gas flows in from the left side of the drawing. Similarly, a stainless steel (SUS) conductive mesh 2 is disposed along the transverse direction on the downstream side (right side) of the central cylindrical portion of the housing 1, and the housing 1 is tapered to the left and right of the central cylindrical portion. Is forming. Further, the discharge electrode 3 is fixed to the wall portion at the upper center of the central cylindrical portion of the housing 1 by existing appropriate fixing means. The discharge electrode 3 hangs an L-shaped discharge part 3b from the insulator 3a inside the housing 1.

  The discharge electrode 3 is connected to a high voltage power source 4 (preferably a variable voltage type), and a voltmeter 6 and an ammeter 7 as current detection means are connected between the discharge electrode 3 and the high voltage power source. Yes. In the vicinity of the upstream entrance of the housing 1, a temperature sensor 5 as exhaust gas temperature detection means is provided, and is configured to always detect the temperature of the exhaust gas flowing in the exhaust purification device. The exhaust gas purification apparatus of the present invention is provided with an electronic control unit (ECU), which is a control means, at an appropriate location. As will be described in detail later, data from the temperature sensor 5 and ammeter 7, and further, an internal combustion engine Data on the rotational speed and fuel injection amount are always transferred from the system, and ON / OFF control of the switch of the high-voltage power supply 4 and setting / control of the applied voltage value or the expected arc discharge occurrence voltage value are performed. In the present invention, the discharge electrode 3 is a negative electrode, and a negative DC high voltage is applied to generate a corona discharge.

  FIG. 3 is a flowchart of high-voltage power supply control by the ECU, which will be described along the stage numbers S1 to S8. The internal combustion engine (engine) is started, the exhaust gas temperature is measured by the temperature sensor, and the exhaust gas temperature data is transferred to the ECU (S1). The ECU determines whether or not the temperature is higher than the condensation temperature (S2). If the temperature is equal to or lower than the condensation temperature, the switch of the high-voltage power supply is not turned on but remains turned off. The switch of the high voltage power supply is turned on only after the temperature equal to or higher than the dew condensation temperature is transferred after a certain time has elapsed, and the preparation for starting the corona discharge is completed in the housing 1.

  Here, the relationship between the exhaust gas temperature and the dew condensation will be described with reference to FIG. If dew condensation occurs on the electrode, it will leak even if energized and corona discharge will not occur. FIG. 4 illustrates the correlation between the temperature at which the electrode condenses, that is, the dew point temperature, and the exhaust gas temperature. The vertical axis indicates the temperature, the horizontal axis indicates the elapsed time after engine start, and the exhaust gas increases with time. It is shown that the temperature is rising. Moreover, in FIG. 4, it turns out that the open air temperature (it shows with a dotted line) is distributed in the range of 50-70 degreeC. Considering especially on the safety side, a temperature of 70 ° C. or less is considered to be a condensation region, and here, 70 ° C. is assumed to be a condensation temperature and set in the ECU. Therefore, when the exhaust gas temperature is 70 ° C. or lower, the switch of the high voltage power source remains OFF, and when it exceeds 70 ° C., the switch is turned ON.

  In the prior art, the exhaust gas temperature was not measured, and therefore, after the engine was started, even if condensation occurred, the high-voltage power supply was automatically turned on and corona discharge did not occur. Although it has been performed, according to the present invention, such useless application is never performed, and thus corona discharge can be generated very efficiently.

  Referring again to FIG. 3, when the exhaust gas temperature reaches the dew condensation temperature of 70 ° C. or higher, the switch of the high-voltage power supply is turned on by a command from the ECU, and the ECU next enters the applied voltage value setting operation (S3, S4). ). When the engine is started, data on the engine speed and the fuel injection amount is separately measured in the engine system and is constantly transferred to the ECU. The ECU calculates the amount of exhaust particulate (PM) contained in the exhaust gas based on the engine speed and the fuel injection amount (S3). In this way, in the ECU, data regarding the exhaust gas temperature and the amount of exhaust particulates (PM) contained in the exhaust gas are always grasped. On the other hand, a map showing the correlation between the exhaust gas temperature and the amount of exhaust particulates (PM) contained in the exhaust gas and the arc discharge generation voltage value is created and input in advance in the ECU. Has been. In the ECU, by calculating and processing the data regarding the exhaust gas temperature and the amount of exhaust particulates (PM) contained in the exhaust gas and the data on the map above, the expected arc discharge occurrence voltage value is calculated. The applied voltage value is always set to be lower than the expected arc discharge occurrence voltage value (S4).

  Here, the correlation between the exhaust gas temperature and the arc discharge generation voltage will be described with reference to FIG. FIG. 5 is an image diagram showing the above-described correlation, where the vertical axis represents the arc discharge generation voltage, the horizontal axis represents the exhaust gas temperature, and the correlation when there are many exhaust particulates (PM) is represented by a solid line. The correlation when (PM) is small is indicated by a dotted line. As is apparent from the figure, first, the higher the exhaust gas temperature, the lower the arc discharge generation voltage, regardless of the amount of exhaust particulates (PM). In other words, the higher the exhaust gas temperature, the lower the arc discharge. It has been shown. Further, it has been clarified that, when compared at the same temperature, arc discharge occurs at a lower voltage when the amount of exhaust particulate (PM) in the exhaust gas is larger than when the amount is small. When arc discharge occurs, the voltage drops during the arc discharge and for a while after that, the corona discharge stops, and the corona discharge performance cannot be obtained at all.

  The ECU always analyzes the data regarding the exhaust gas temperature and the amount of exhaust particulate matter (PM) contained in the exhaust gas and the data on the map above, and always falls below the expected arc discharge occurrence voltage value calculated. An applied voltage value is set in a range (S4), and a corona discharge is generated in the exhaust purification device by applying the set voltage (S5). Thereafter, the ammeter continues to check whether or not the arc discharge state has occurred, and the steady operation is continued unless arc discharge occurs (S6, S7). That is, the amount of exhaust particulates (PM) is calculated based on the engine speed and fuel injection amount that are continuously transferred in the ECU, and is applied within the range that is always below the expected voltage value of arc discharge generation by matching with the map together with the temperature data. A voltage value is set and voltage application is performed (S3 to S7 are repeated). When the arc state is confirmed by the ammeter (S7), the applied voltage value is reduced by a predetermined amount in the ECU to control to decrease to a voltage value at which no arc discharge occurs (S8). After reducing the voltage, the ammeter is used again to check whether or not an arc condition has occurred, and if necessary, the same process is repeated in the ECU until it is confirmed that no arc condition has occurred (S6 to S6). S8).

  FIG. 6 shows another embodiment of the present invention, and is an enlarged view of the exhaust purification device shown in FIG. Stainless steel (SUS) exhaust purification device housing 1, stainless steel (SUS) conductive net 2, discharge electrode 3, high voltage power supply (not shown), ECU, etc. are exactly the same as those of the previous embodiment. As a dew condensation detection means, a humidity sensor is incorporated in place of the temperature sensor. Therefore, it is configured to control ON / OFF of the switch of the high voltage power source using the set outdoor humidity instead of the dew point temperature.

  Thus, because of the above configuration, the high-pressure power switch is turned on only in the range of the temperature to which the voltage should be applied by always measuring the exhaust gas temperature during operation and checking the detected exhaust gas temperature. The switch is turned off under conditions other than the above, and the appropriate applied voltage value can be set based on changes in the exhaust gas temperature. If arc discharge occurs unexpectedly, the applied voltage value is automatically It is configured such that it can be controlled to fall to a non-discharge voltage value. For this reason, according to the present invention, it is possible to control the generation of corona discharge very efficiently, and as a result, a practical internal combustion engine capable of aggregating and collecting exhaust particulates (PM) extremely efficiently. An exhaust treatment device can be realized.

1 is a schematic system configuration diagram of an internal combustion engine system incorporating an exhaust emission control device according to an embodiment of the present invention. 1 is an overall configuration diagram of an exhaust emission control device for an internal combustion engine in an embodiment of the present invention. 3 is a flowchart for high voltage power supply control by an ECU in an exhaust gas purification apparatus for an internal combustion engine in an embodiment of the present invention. It is the image figure which showed the relationship between the exhaust gas temperature and dew condensation in embodiment of this invention. It is the image figure which showed the relationship between the exhaust gas temperature and arc discharge generation voltage in embodiment of this invention. It is a whole block diagram of the exhaust gas purification apparatus for internal combustion engines in other embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Conductive net | network 3 Discharge electrode 3a insulator 3b Discharge part 4 High voltage power supply 5 Temperature sensor 6 Voltmeter 7 Ammeter 8 ECU
9 Humidity sensor

Claims (15)

  In an exhaust purification device for an internal combustion engine, a high voltage is applied between electrodes in an exhaust part of an internal combustion engine to generate corona discharge to charge exhaust particulates, and agglomerate and collect the charged exhaust particulates. An exhaust emission control device, comprising a gas temperature detection means and a high-voltage power supply, and comprising a control means for controlling the high-voltage power switch to ON or OFF based on the detected exhaust gas temperature.   2. The exhaust gas purification according to claim 1, wherein the control means controls the high pressure power switch to be turned off when the detected exhaust gas temperature is lower than the dew condensation temperature of the electrode portion, and to turn on the high voltage power switch when the temperature is higher. apparatus.   The exhaust emission control device according to claim 2, wherein the dew condensation temperature is 50 to 70 ° C.   In an exhaust purification device for an internal combustion engine, a high voltage is applied between electrodes in an exhaust part of an internal combustion engine to generate corona discharge to charge exhaust particulates, and agglomerate and collect the charged exhaust particulates. An exhaust gas purification apparatus comprising a control means for providing a gas temperature detecting means and a voltage variable high voltage power source and controlling an applied voltage value based on a detected exhaust gas temperature.   The exhaust emission control device according to claim 4, wherein the applied voltage value is set to be equal to or less than an expected arc discharge occurrence voltage value.   6. The exhaust emission control device according to claim 5, wherein the expected arc discharge occurrence voltage value is calculated from the detected exhaust gas temperature and the amount of exhaust particulates (PM) determined by operating conditions of the internal combustion engine.   The exhaust emission control device according to claim 6, wherein the operating conditions of the internal combustion engine are an internal combustion engine speed and a fuel injection amount.   In an exhaust purification device for an internal combustion engine, a high voltage is applied between electrodes in an exhaust part of an internal combustion engine to generate corona discharge to charge exhaust particulates, and agglomerate and collect the charged exhaust particulates. Gas temperature detection means and voltage variable high-voltage power supply are provided, control means for controlling the voltage variable high-voltage power switch to ON or OFF based on the detected exhaust gas temperature, and controlling the applied voltage value based on the detected exhaust gas temperature. An exhaust emission control device characterized by that.   The control means controls to turn off the voltage variable high voltage power switch when the detected exhaust gas temperature is lower than the dew condensation temperature of the electrode portion, and to turn on the voltage variable high voltage power switch when it is higher. The exhaust emission control device described.   The exhaust emission control device according to claim 9, wherein the dew condensation temperature is 50 to 70 ° C.   The exhaust gas purification apparatus according to any one of claims 8 to 10, wherein the applied voltage value is set to be equal to or less than an expected arc discharge occurrence voltage value.   12. The exhaust emission control device according to claim 11, wherein the expected arc discharge occurrence voltage value is calculated from the detected exhaust gas temperature and the amount of exhaust particulates (PM) determined by operating conditions of the internal combustion engine. The exhaust emission control device according to claim 12, wherein the operating condition of the internal combustion engine is an internal combustion engine speed and a fuel injection amount.   In an exhaust purification device for an internal combustion engine, a high voltage is applied between electrodes in an exhaust part of an internal combustion engine to generate corona discharge to charge exhaust particulates, and agglomerate and collect the charged exhaust particulates. Gas temperature detection means, current detection means and voltage variable high voltage power supply are installed, voltage variable high voltage power switch is controlled to ON or OFF based on detected exhaust gas temperature, applied voltage value is controlled based on detected exhaust gas temperature, and An exhaust emission control device comprising control means for controlling the applied voltage value to drop to an arc discharge non-generated voltage value based on arc discharge detection by a current detection means.   4. An exhaust gas humidity detection means is provided instead of the exhaust gas temperature detection means, and the control means controls the high-voltage power switch to be turned on or off based on the detected exhaust gas humidity. The exhaust emission control device according to any one of 8 to 14.

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