JP2012219677A - Particulate-matter processing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress flowing of an excessive current due to condensed water deposited on an electrode.SOLUTION: A particulate-matter processing device includes: an electrode provided in an exhaust passage of an internal combustion engine; a power supply connected to the electrode in order to apply a voltage thereto; a detection device for detecting a current flowing through the electrode; and an applied-voltage reducing device that reduces the voltage, applied from the power supply to the electrode, when the current to be detected by the detection device exceeds a prescribed value compared with when it is less than the prescribed value.

Description

  The present invention relates to a particulate matter processing apparatus.

  When the current passing through the discharge electrode is equal to or greater than a predetermined value, it is determined that particulate matter (hereinafter also referred to as PM) is attached to the discharge electrode, and the applied voltage is increased to remove PM from the discharge electrode. The technique to make is known (for example, refer patent document 1). The removal of deposits from the electrode is called electrode regeneration.

  In addition, a technique for determining a failure of the PM sensor based on a change in capacitance of the sensor electrode part due to the condensed water generated in the exhaust pipe immediately after the engine starts adheres to the sensor electrode part is known ( For example, see Patent Document 2.)

  In addition, a technique is known in which a discharge electrode is provided in an exhaust passage of an internal combustion engine, and corona discharge is generated from the discharge electrode to charge the PM to aggregate the PM (see, for example, Patent Document 3). By aggregating PM, the number of PM particles can be reduced. Moreover, since the particle diameter of PM becomes large, when a filter is provided on the downstream side, PM is easily collected by the filter.

  Here, when the water contained in the exhaust is condensed and adheres to the electrode, electricity flows between the electrode and the exhaust passage through the condensed water. For this reason, the electric current which flows through an electrode becomes large, and there exists a possibility that the members which comprise particulate matter processing apparatuses, such as a power supply, an electrode, and another circuit, may deteriorate or fail. Further, if the apparatus is configured to withstand a large current, the cost increases. Further, when the current increases, the power consumption increases, and the fuel consumption may deteriorate.

JP 2006-105081 A JP 2010-275917 A JP 2006-194116 A

  The present invention has been made in view of the above-described problems, and an object of the present invention is to prevent an excessive current from passing through the condensed water adhering to the electrode.

In order to achieve the above object, the particulate matter processing apparatus according to the present invention is:
An electrode provided in an exhaust passage of the internal combustion engine;
A power source connected to the electrode for applying a voltage;
A detection device for detecting a current through the electrode;
When the current detected by the detection device is equal to or greater than a predetermined value, an applied voltage reduction device that reduces the voltage applied from the power source to the electrode than when the current is less than a predetermined value;
Is provided.

Here, when voltage is applied to the electrodes, PM can be charged. The charged PM moves toward the inner wall of the exhaust passage due to the Coulomb force or the flow of exhaust. Since the PM that has reached the inner wall of the exhaust passage emits electrons to the exhaust passage, electricity flows to the ground side from the electrode. And since PM which emitted the electron aggregates with other PM which exists near, the number of particles can be decreased.

  By the way, when water adheres to the electrode, it becomes difficult to charge PM floating in the exhaust gas, and it is difficult to aggregate the PM. On the other hand, when electricity flows between the electrode and the exhaust passage through the water attached to the electrode, the current detected by the detection device increases. And the electric current which passes through the water adhering to an electrode is larger than the electric current which passes when coagulating PM which is floating in exhaust_gas | exhaustion. Therefore, it is possible to determine whether or not water has adhered to the electrode (whether or not the electrode has been wetted) by this increase in current. The water adhering to the electrode is a condensed water in the exhaust. Therefore, when the current detected by the detection device is increased in an operation state where condensed water can be generated, it may be determined that water is attached to the electrode.

  Here, if excessive electricity flows between the electrode and the exhaust passage through the condensed water, members constituting the particulate matter processing apparatus such as the power source and the electrode may be deteriorated or broken down. On the other hand, when the current is greater than or equal to a predetermined value, the applied voltage is made smaller than when the current is less than the predetermined value. Thereby, since it becomes difficult to flow an electric current, an apparatus can be protected. That is, it is possible to prevent an excessive current from passing through the electrode. The predetermined value may be a lower limit value of the current detected when water is attached to the electrode. A value obtained by giving a certain margin to the lower limit value may be set as the predetermined value. Moreover, it is good also as a value when an electric current exceeds an allowable range.

  In the present invention, the applied voltage reducing device can stop the application of voltage to the electrode when the current detected by the detecting device is equal to or greater than the predetermined value.

  As a result, no current flows through the electrode, and no excessive current is generated. Therefore, it is possible to prevent an excessive current from passing more reliably. On the other hand, by applying a voltage smaller than usual to the electrode, the aggregation of PM can be promoted although the amount is small.

In the present invention, an electrical resistance calculation device that calculates electrical resistance based on the current detected by the detection device;
A water removal determination device that determines that water has been removed from the electrode when the electrical resistance calculated by the electrical resistance calculation device is equal to or greater than a predetermined value;
Can be provided.

  Even if water adheres to the electrode, if the temperature of the exhaust passage or the electrode subsequently increases, the water evaporates from the electrode. Aggregation of PM can be promoted by increasing the applied voltage after water has evaporated from the electrode. Here, when water adheres to the electrode, the electrical resistance decreases. This electrical resistance can be calculated based on the applied voltage and the detected current. Therefore, based on the calculated electrical resistance, it can be determined whether water is attached to the electrode. If the electrical resistance when water is removed from the electrode is set in advance as a predetermined value, it can be determined that the water has been removed from the electrode when the electrical resistance is equal to or greater than the predetermined value. Thereby, since the applied voltage can be quickly increased, the aggregation of PM can be promoted.

In the present invention, an estimation device that estimates the amount of water evaporated from the electrode based on the operating state of the internal combustion engine;
A water removal determination device that determines that water has been removed from the electrode when the amount of water estimated by the estimation device exceeds a predetermined value;
Can be provided.

  Here, since the temperature of the exhaust passage and the electrode changes according to the operating state of the internal combustion engine, the evaporation amount of water attached to the electrode can be calculated based on the operating state of the internal combustion engine. Since there is a limit on the amount of water adhering to the electrode, if this limit is set as a predetermined value, when the amount of water estimated to have evaporated exceeds the predetermined value, Can be determined to have been removed. Thereby, since the applied voltage can be quickly increased, the aggregation of PM can be promoted.

  Note that the amount of water adhering to the electrode can be estimated, and it can be determined that the water has been removed from the electrode when the amount of water becomes a predetermined value or less. This predetermined value can be an adhesion amount of water that can be assumed that water has been removed from the electrode, or an adhesion amount of water that does not cause an excessive current to flow even when a voltage is applied to the electrode. The predetermined value in this case may be 0.

In the present invention, a processing unit provided in the exhaust passage and provided with the electrode;
An insulating part for insulating electricity between the processing part and the exhaust passage;
A grounding unit for grounding the processing unit;
A pulse current determination device for determining whether or not a pulse current is generated in the current detected by the detection device;
With
The detection device detects a current at the grounding unit,
When the current detected by the detection device is less than the predetermined value, the voltage applied to the electrode is increased until the pulse current determination device determines that a pulse current has been generated, and the pulse current determination device A pulse current suppressing device that adjusts the voltage applied to the electrode to be lower than the voltage at which the pulse current is generated by reducing the voltage applied to the electrode when it is determined that a pulse current has occurred. it can.

  When the voltage applied to the electrode is increased, more electrons are emitted from the electrode. For this reason, since aggregation of PM can be promoted, the number of particles of PM can be further reduced. However, if the voltage applied to the electrode is too high, strong discharge such as corona discharge or arc discharge can occur. When such a strong discharge occurs, PM is miniaturized by high-speed electrons. Therefore, the applied voltage is not necessarily increased.

  For this reason, the applied voltage is set so that strong discharge does not occur when a voltage is applied. Note that PM can be agglomerated even at an applied voltage that does not cause strong discharge such as corona discharge or arc discharge. Here, when the current is detected in the ground portion, the pulse current is detected when a strong discharge is generated in the electrode. That is, if a voltage is applied so as not to generate a pulse current, generation of strong discharge can be suppressed.

  For example, the applied voltage is gradually increased, and the applied voltage is reduced when a pulse current is generated. Thereby, since it can suppress that a strong discharge generate | occur | produces, it can suppress that PM is refined | miniaturized.

  Further, the PM is more easily aggregated by increasing the applied voltage in a range where no pulse current is generated. That is, PM aggregation can be promoted by increasing the applied voltage within a range where no pulse current is generated. For this reason, feedback control may be performed so that the applied voltage becomes maximum within a range in which no pulse current is generated.

Note that the detection device detects a current on the potential reference point side of the electrode. Generally, on the power supply side from the electrode, the wiring is longer or thicker than the electrode on the ground side. In addition, charges may be stored on the power supply side of the electrode. Then, if a current is detected on the power supply side of the electrode, even if a strong discharge occurs in the electrode, the current detected by the detection device rises and falls slowly. For this reason, it may be difficult to detect the pulse current.

  On the other hand, on the ground side from the electrode, the wiring can be made relatively short and thin. For this reason, when the current is detected on the ground side from the electrode, it is easy to detect the pulse current when a strong discharge occurs. Therefore, by detecting the current on the ground side with respect to the electrode, it is possible to more reliably detect that a strong discharge has occurred.

  Moreover, it can suppress that electricity flows other than a grounding part by providing an insulating part. For this reason, the pulse current can be detected more accurately when a strong discharge occurs.

  Then, after the water is removed from the electrode, even if the applied voltage is increased until the pulse current is detected, an excessive current does not pass through, so that the optimum applied voltage can be adjusted. Note that the maximum value of the pulse current detected after water is removed from the electrode is smaller than the current detected when water is attached to the electrode.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that an excessive electric current passes with the condensed water adhering to an electrode.

It is a figure which shows schematic structure of the particulate matter processing apparatus which concerns on an Example. 3 is a flowchart illustrating a control flow of an applied voltage according to the first embodiment. 6 is a flowchart illustrating a control flow of an applied voltage according to a second embodiment. 10 is a flowchart showing a control flow of an applied voltage according to a third embodiment. 10 is a flowchart illustrating a control flow of an applied voltage according to a fourth embodiment.

  Hereinafter, specific embodiments of the particulate matter processing apparatus according to the present invention will be described with reference to the drawings.

Example 1
FIG. 1 is a diagram illustrating a schematic configuration of a particulate matter processing apparatus 1 according to the present embodiment. The particulate matter processing apparatus 1 is provided in, for example, an exhaust passage 2 of a gasoline engine. It can also be provided in the exhaust passage of a diesel engine.

  The particulate matter processing apparatus 1 includes a housing 3 whose both ends are connected to an exhaust passage 2. The material of the housing 3 is a stainless steel material. The housing 3 is formed in a hollow cylindrical shape having a diameter larger than that of the exhaust passage 2. Both ends of the housing 3 are formed in a tapered shape in which the cross-sectional area decreases as the distance from the end increases. In FIG. 1, the exhaust flows through the exhaust passage 2 in the direction of the arrow and flows into the housing 3. For this reason, the housing 3 may be a part of the exhaust passage 2. In the present embodiment, the housing 3 corresponds to the processing section in the present invention.

The exhaust passage 2 and the housing 3 are connected via an insulating portion 4. The insulating part 4 is made of an electrical insulator. The insulating portion 4 is sandwiched between a flange 21 formed at the end of the exhaust passage 2 and a flange 31 formed at the end of the housing 3. The exhaust passage 2 and the housing 3 are fastened by bolts and nuts, for example. In addition, these bolts and nuts are also insulated so that electricity does not flow through these bolts and nuts. In this way, electricity is prevented from flowing between the exhaust passage 2 and the housing 3.

  An electrode 5 is attached to the housing 3. The electrode 5 penetrates the side surface of the housing 3, extends from the side surface of the housing 3 toward the central axis of the housing 3, bends in the vicinity of the central axis, and upstream of the flow of exhaust gas, and is parallel to the central axis It extends toward the upstream side of the exhaust flow. For this reason, the end of the electrode 5 is located near the central axis of the housing 3. Further, an insulator 51 made of an electrical insulator is provided on the electrode 5 so that electricity does not flow between the electrode 5 and the housing 3. The insulator 51 is located between the electrode 5 and the housing 3, and has a function of insulating electricity and fixing the electrode 5 to the housing 3.

  The electrode 5 is connected to the power source 6 via the power source side electric wire 52. The power source 6 can energize the electrode 5 and change the applied voltage. The power source 6 is connected to the control device 7 and the battery 8 through electric wires. The control device 7 controls the voltage that the power source 6 applies to the electrode 5.

  A ground side electric wire 53 is connected to the housing 3, and the housing 3 is grounded via the ground side electric wire 53. The ground side electric wire 53 is provided with a detection device 9 that detects a current passing through the ground side electric wire 53. For example, the detection device 9 detects a current by measuring a potential difference between both ends of a resistor provided in the middle of the ground-side electric wire 53. The detection device 9 is connected to the control device 7 via an electric wire. Then, the current detected by the detection device 9 is input to the control device 7. In the present embodiment, the ground side electric wire 53 corresponds to the ground portion in the present invention.

  Note that an accelerator opening sensor 71, a crank position sensor 72, an engine temperature sensor 73, an air flow meter 74, an outside air temperature sensor 75, and an exhaust passage temperature sensor 76 are connected to the control device 7. The accelerator opening sensor 71 outputs an electrical signal corresponding to the amount of depression of the accelerator pedal by the driver of the vehicle on which the internal combustion engine is mounted, and detects the engine load. The crank position sensor 72 detects the engine speed. The engine temperature sensor 73 detects the temperature of the internal combustion engine by detecting the temperature of the cooling water of the internal combustion engine or the temperature of the lubricating oil. The air flow meter 74 detects the intake air amount of the internal combustion engine. The outside air temperature sensor 75 detects the temperature of outside air. The exhaust passage temperature sensor 76 is attached to the exhaust passage 2 upstream of the housing 3 and detects the temperature of the exhaust passage 2.

  In the particulate matter processing apparatus 1 configured as described above, electrons are emitted from the electrode 5 by applying a negative DC high voltage from the power source 6 to the electrode 5. That is, electrons are emitted from the electrode 5 by making the potential of the electrode 5 lower than that of the housing 3. The electrons in the exhaust gas can be negatively charged by the electrons. Negatively charged PM moves due to Coulomb force and gas flow. When the PM reaches the housing 3, the electrons that have negatively charged the PM are emitted to the housing 3. The PM that has released electrons to the housing 3 aggregates to increase the particle size. Moreover, the number of PM particles is reduced due to aggregation of PM. That is, by applying a voltage to the electrode 5, the particle diameter of PM can be increased and the number of PM particles can be reduced.

In the present embodiment, the electrode 5 is bent toward the upstream side of the exhaust flow, but instead, it may be bent toward the downstream side. Here, when the electrode 5 is bent toward the upstream side of the exhaust flow as in the present embodiment, PM hardly adheres to the insulator portion 51. That is, since PM can be charged on the upstream side of the insulator portion 51, the PM moves toward the inner peripheral surface of the housing 3. For this reason, since PM colliding with the insulator part 51 decreases, it becomes difficult for PM to adhere to the insulator part 51. However, if the electrode 5 is bent toward the upstream side of the exhaust flow, the electrode 5 is easily deformed by receiving a force from the exhaust flow. For this reason, it is suitable when the electrode 5 is short. On the other hand, when the electrode 5 is bent toward the downstream side of the exhaust flow, PM is likely to adhere to the insulator portion 51, but the electrode 5 is not easily deformed even if a force is received from the exhaust flow. For this reason, durability and reliability are high and the electrode 5 can be lengthened.

  By the way, when the water condensed in the exhaust passage 2 adheres to the electrode 5 including the insulator portion 51, the insulating property of the electrode 5 is lowered. And electricity can flow between the electrode 5 and the housing 3 through this water. For this reason, the electric current which flows through the electrode 5 becomes large, and there exists a possibility that the members which comprise the particulate matter processing apparatus 1, such as the power supply 6, the electrode 5, and other circuits, may deteriorate or break down. Further, since electricity flows through water, electrons emitted from the electrode 5 are reduced, so that it is difficult to charge PM floating in the exhaust gas, and it is difficult to aggregate PM.

  Therefore, it is determined that water is attached to the electrode 5 based on the current detected by the detection device 9, and when it is determined that water is attached to the electrode 5, the applied voltage can be reduced, Alternatively, the voltage application is stopped. Here, when electricity is not flowing between the electrode 5 and the housing 3 via water, the current changes according to the amount of PM floating in the exhaust gas. The current detected at this time is relatively small. On the other hand, the current detected when the current passes through the water adhering to the electrode 5 is relatively large. Therefore, it can be determined that water is attached to the electrode 5 when the detected current is equal to or greater than a predetermined value. The predetermined value is obtained in advance by experiments or the like as the lower limit value of the detected current when the current passes through the water adhering to the electrode 5.

  In addition, since the insulation part 4 is provided in a present Example, it is suppressed that electricity passes to the exhaust passage 2. FIG. Therefore, the current passing through the housing 3 through the water adhering to the electrode 5 and the PM floating in the exhaust gas is detected by the detection device 9. Further, by detecting the current in the ground side electric wire 53, the current detection accuracy can be increased. In general, the power supply side electric wire 52 is longer or thicker than the ground side electric wire 53. Then, if a current is detected in the power supply side electric wire 52, the rise and fall of the detected current with respect to the actual current change becomes slow. For this reason, there exists a possibility that the detection accuracy of an electric current may become low.

  On the other hand, in the ground side electric wire 53, wiring can be made relatively short and thin. For this reason, the response to the actual change in current is higher when the current is detected in the ground-side electric wire 53. Therefore, the current can be detected more accurately by detecting the current in the ground side electric wire 53. However, the current can also be detected in the power supply side electric wire 52.

  Next, FIG. 2 is a flowchart showing a control flow of the applied voltage according to the present embodiment. This routine is repeatedly executed by the control device 7 every predetermined time.

  In step S101, the operating state of the internal combustion engine is acquired. For example, values necessary for the subsequent processing, such as engine speed, engine load, and internal combustion engine temperature, are read. The engine speed is detected by a crank position sensor 72, and the engine load is detected by an accelerator opening sensor 71. Further, the temperature of the internal combustion engine (for example, the temperature of the lubricating oil or the temperature of the cooling water) is detected by the engine temperature sensor 73.

In step S102, the voltage applied to the electrode 5 is calculated. The applied voltage is set according to the estimated number of PM particles (number / cm ³ ). The number of PM particles is the number of PM particles discharged from the internal combustion engine, and is the number of PM particles before flowing into the housing 3. Since the number of PM particles is correlated with the engine speed, the engine load, and the temperature of the internal combustion engine (for example, the temperature of the lubricating oil or the temperature of the cooling water), the number of PM particles is calculated based on these values. A plurality of maps for calculating the number of PM particles may be stored according to the temperature of the internal combustion engine from the engine speed and the engine load, and the number of PM particles may be calculated based on the map.

  A sensor for detecting the number of PM particles may be attached to the exhaust passage 2 on the upstream side of the housing 3 and the number of PM particles may be detected by the sensor.

  Then, the applied voltage is calculated based on the number of PM particles and the exhaust gas amount (g / sec) of the internal combustion engine. This relationship may be obtained in advance by experiments or the like and mapped. Since the exhaust gas amount of the internal combustion engine has a correlation with the intake air amount of the internal combustion engine, it can be obtained based on the intake air amount detected by the air flow meter 74.

  Here, since the inertia force of PM becomes smaller as the amount of exhaust gas is smaller, the influence of electrostatic action becomes relatively larger. For this reason, PM tends to aggregate. Therefore, as the amount of exhaust gas decreases, PM aggregates with a smaller applied voltage. For this reason, the applied voltage is reduced as the amount of exhaust gas decreases. Also, the greater the number of PM particles, the shorter the distance between the PM particles, so that the influence of electrostatic action becomes relatively large. Therefore, as the number of PM particles increases, PM aggregates with a smaller applied voltage. For this reason, the applied voltage is decreased as the number of PM particles is increased.

  Further, the applied voltage may be a value such that the reduction rate of the number of PM particles becomes a predetermined value (for example, 40%). The applied voltage may be a predetermined value that is determined in advance. Furthermore, the applied voltage may be increased as much as possible within a range where no pulse current is generated.

  Then, after the applied voltage is calculated, this voltage is applied, the process proceeds to step S103, and the detected current is acquired. This detected current is a value detected by the detection device 9.

  In step S104, the outside air temperature is acquired. This outside air temperature is obtained by the outside air temperature sensor 75.

  In step S105, the temperature of the exhaust passage 2 is acquired. The temperature of the exhaust passage 2 is obtained by an exhaust passage temperature sensor 76. Note that the temperature of the exhaust passage 2 may be estimated based on the operating state of the internal combustion engine and the outside air temperature.

  In step S106, it is estimated whether condensed water is produced | generated. This is estimated based on whether or not a condition for generating condensed water in the exhaust passage 2 is satisfied. In this step, it is not estimated whether water is attached to the electrode 5, but is estimated whether liquid water exists in the exhaust passage 2. Since condensed water is generated when the temperature of the exhaust passage 2 is relatively low, it can be estimated that condensed water is generated when the temperature of the exhaust passage 2 is equal to or lower than a threshold value. This threshold value is obtained in advance by experiments or the like as the upper limit value of the temperature of the exhaust passage 2 where condensed water is generated. Further, it may be estimated that condensed water is generated for a predetermined period from the start of the internal combustion engine. Further, whether or not water is condensed in the exhaust passage 2 is determined by the temperature of the exhaust, the temperature of the outside air, the operating state of the internal combustion engine, and the like, so the conditions for generating the condensed water may be mapped. Moreover, you may estimate whether condensed water is produced | generated by a known technique.

  In step S107, it is determined whether or not it is estimated that condensed water has been generated in step S106. That is, it is determined whether or not there is a possibility that water adheres to the electrode 5. If an affirmative determination is made in step S107, the process proceeds to step S108, and if a negative determination is made, there is no possibility of current passing through the water attached to the electrode 5, so this routine is terminated. Note that it is possible to determine whether or not condensed water has been generated in this step because, for example, the detection current may increase due to the influence of PM adhering to the electrode 5 and unburned fuel contained in the exhaust. This is to distinguish them from these.

  In step S108, it is determined whether or not the detected current acquired in step S103 is greater than or equal to a predetermined value A. The predetermined value A is a lower limit value of the current detected when water is attached to the electrode 5, and is sufficiently larger than the current detected when water is not attached to the electrode 5. . If an affirmative determination is made in step S108, the process proceeds to step S109. If a negative determination is made, water does not adhere to the electrode 5, and this routine is terminated.

  In step S109, the application of voltage to the electrode 5 is stopped. Thereby, it can suppress that an excessive electric current flows. In this step, the applied voltage may be made smaller than when no water is attached to the electrode 5. The applied voltage at this time may be a predetermined value set in advance so that an excessive current does not flow, or may be set based on the detected current. In addition, the applied voltage may be feedback controlled so that the detected current is within a predetermined range. In this embodiment, the control device 7 that processes step S109 corresponds to the applied voltage reducing device in the present invention.

  As described above, according to the present embodiment, when water adheres to the electrode 5, the applied voltage is reduced or the application of the voltage is stopped, so that an excessive current can be prevented from flowing. Thereby, it can suppress that the particulate matter processing apparatus 1 deteriorates or fails.

(Example 2)
In this embodiment, a condition for increasing the applied voltage after the applied voltage is reduced or after the application of the voltage is stopped is set. Since other devices are the same as those in the first embodiment, the description thereof is omitted.

  Here, when the operation time of the internal combustion engine becomes longer, the condensed water in the exhaust passage 2 evaporates. Therefore, even if water adheres to the electrode 5, this water is removed over time. When water is removed in this way, the applied voltage can be quickly increased to promote PM aggregation.

  The amount of evaporation of water adhering to the electrode 5 is determined by the temperature of the exhaust, the temperature of the outside air, the operating state of the internal combustion engine, and the like. These relationships may be obtained in advance by experiments or the like. These relationships may be mapped. Further, the evaporation amount of water may be obtained by a known technique. It is considered that the water has been removed from the electrode 5 when the amount of water evaporation has increased sufficiently.

  Next, FIG. 3 is a flowchart showing a control flow of the applied voltage according to the present embodiment. This routine is repeatedly executed by the control device 7 every predetermined time. In addition, steps that perform the same processing as the flow shown in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In this routine, step S201 is executed after step S109. In step S201, the evaporation amount of water adhering to the electrode 5 is calculated. The amount of water evaporation is calculated based on a map stored in advance. In the present embodiment, the control device 7 that processes step S201 corresponds to the estimation device according to the present invention.

In step S202, it is determined whether the evaporation amount calculated in step S201 is equal to or greater than a predetermined value B. The predetermined value B is obtained in advance by experiments or the like as a value that is necessary and sufficient for the amount of evaporation of water adhering to the electrode 5. That is, since the amount of water adhering to the electrode 5 is not calculated, the amount of water remaining on the electrode 5 cannot be calculated at this time, but the amount of water adhering to the electrode 5 is Since there is a limit, if it is determined that the amount of water exceeding this limit has evaporated, no water remains on the electrode 5. That is, in this step, it is determined whether or not water is removed from the electrode 5. If an affirmative determination is made in step S202, the process proceeds to step S203, and if a negative determination is made, the process returns to step S201. In the present embodiment, the control device 7 that processes step S202 corresponds to the water removal determination device in the present invention.

  In step S203, application of a voltage to the electrode 5 is started. The applied voltage at this time is obtained in the same manner as in step S102.

  By the way, when the negative voltage applied to the electrode 5 is increased, more electrons are emitted from the electrode 5. For this reason, since aggregation of PM can be promoted, the number of particles of PM can be further reduced. However, if the voltage applied to the electrode 5 is increased too much, strong discharge such as corona discharge or arc discharge can occur. When such a strong discharge occurs, PM is miniaturized by high-speed electrons. Therefore, in order to promote the aggregation of PM, the voltage may be adjusted to a voltage lower than that of strong discharge such as corona discharge. Here, when a strong discharge such as a corona discharge occurs, the detection device 9 detects a pulse current.

  Therefore, in this embodiment, the applied voltage may be adjusted to a range where no pulse current is generated. In this case, a voltage smaller than the applied voltage that generates the pulse current is applied to the electrode 5. Thereby, generation | occurrence | production of a pulse current is suppressed and it suppresses that the particle number of PM increases. Therefore, the applied voltage is increased until the pulse current is generated, and the applied voltage at which the pulse current starts to be generated is detected. In this embodiment, the control device 7 that detects the applied voltage at which the pulse current starts to be generated corresponds to the pulse current determination device in the present invention. Then, by reducing the voltage applied to the electrode 5 when the pulse current is generated, the voltage applied to the electrode 5 is adjusted to be lower than the voltage at which the pulse current is generated. Note that before the pulse current is generated, a sign that the pulse current is generated may be read from the current to detect the applied voltage at which the pulse current is generated. Moreover, it is good also as an applied voltage used as the boundary of whether a pulse current generate | occur | produces. In this embodiment, the control device 7 that controls the applied voltage in this way corresponds to the pulse current suppressing device of the present invention.

  In the present embodiment, since the insulating portion 4 is provided and the current is detected in the ground side electric wire 53, the pulse current can be detected more accurately.

  As described above, according to the present embodiment, voltage application can be started immediately after water evaporates from the electrode 5, so that aggregation of PM can be promoted.

(Example 3)
In this embodiment, the condition for increasing the applied voltage after reducing the applied voltage is set based on the electrical resistance. Moreover, when condensed water is adhering to the electrode 5, an excessive current is prevented from passing by gradually reducing the applied voltage. Since other devices are the same as those in the first embodiment, the description thereof is omitted.

  Here, the electrical resistance changes according to the amount of water adhering to the electrode 5. That is, the electrical resistance increases when no water is present, but the electrical resistance decreases when water is present and electricity flows between the electrode 5 and the housing 3 through the water. Therefore, if the electrical resistance increases, it can be estimated that the water adhering to the electrode 5 is evaporated and the insulating property of the electrode 5 is restored.

  Next, FIG. 4 is a flowchart showing a control flow of the applied voltage according to the present embodiment. This routine is repeatedly executed by the control device 7 every predetermined time. In addition, steps in which the same processing as in the flow shown in the first or second embodiment is performed are denoted by the same reference numerals and description thereof is omitted.

  In this routine, when an affirmative determination is made in step S108, the process proceeds to step S301. In step S301, the applied voltage is reduced. The amount of reduction of the applied voltage at this time is set in advance as a value suitable for detecting an applied voltage through which an excessive current does not pass. That is, if the reduction amount of the applied voltage is too small, the voltage must be reduced many times before the current drops, and therefore it takes time and the device may break down during this time. On the other hand, if the applied voltage is reduced too much, the time until the current drops can be shortened, but the applied voltage becomes too low and PM aggregation becomes difficult. Therefore, the reduction amount of the applied voltage may be determined based on the required time and the required accuracy. In this embodiment, the control device 7 that processes step S301 corresponds to the applied voltage reducing device in the present invention.

  In step S302, it is determined whether or not the detected current is a predetermined value C or less. The detected current at this time is a detected current after the applied voltage is reduced in step S301. By step S301 and step S302, the applied voltage is reduced until the detected current becomes a predetermined value C or less. The predetermined value C is a value smaller than the predetermined value A, and can be an upper limit value of the detection current that does not cause a failure of the apparatus. Alternatively, the upper limit value of the allowable detection current may be set. That is, when the detected current is equal to or less than the predetermined value C, the current passing through the electrode 5 is within the allowable range. That is, by reducing the applied voltage so that the detected current is equal to or less than the predetermined value C, it is possible to suppress the occurrence of a failure in the power source 6 or the like. If a positive determination is made in step S302, the process proceeds to step S303, and if a negative determination is made, the process returns to step S301.

  In step S303, the electrical resistance R is calculated. The electric resistance R may be an electric resistance between the electrode 5 and the housing 3, or may be an electric resistance of the entire circuit. The electrical resistance R is calculated based on the detected current and the applied voltage. You may obtain | require the electrical resistance of another apparatus or an electric wire beforehand by experiment. In this embodiment, the control device 7 that processes step S303 corresponds to the electrical resistance calculation device according to the present invention.

  In step S304, it is determined whether or not the electrical resistance R calculated in step S303 is greater than or equal to a predetermined value D. In this step, it is determined whether or not the water adhering to the electrode 5 is evaporated and the electric resistance R is sufficiently large. That is, the predetermined value D is a lower limit value of the electrical resistance when water adhering to the electrode 5 evaporates. When the electrical resistance R is equal to or greater than the predetermined value D, it can be determined that water has been removed from the electrode 5. If an affirmative determination is made in step S304, the process proceeds to step S305. On the other hand, if a negative determination is made in step S304, the process returns to step S303. That is, the electrical resistance R is repeatedly calculated until the electrical resistance R becomes equal to or greater than the predetermined value D. In this embodiment, the control device 7 that processes step S304 corresponds to the water removal determination device in the present invention.

  In step S305, the applied voltage is increased. The applied voltage set at this time is the applied voltage calculated in step S102. Further, the applied voltage may be controlled so that the applied voltage is as large as possible within a range where no pulse current is generated.

  As described above, according to the present embodiment, when water adheres to the electrode 5, the applied voltage is reduced so that an excessive current does not pass, thereby causing a failure of the apparatus while aggregating PM. This can be suppressed. Moreover, since it can be determined that water has evaporated from the electrode 5 based on the electrical resistance, the voltage can be increased immediately thereafter, so that aggregation of PM can be promoted.

Example 4
In this embodiment, the applied voltage is reduced when the amount of water adhering to the electrode 5 is large. Further, when PM is attached to the electrode 5, the electrode 5 is regenerated. Since other devices are the same as those in the first embodiment, the description thereof is omitted.

  Here, when PM adheres to the electrode 5, an excessive current may flow as in the case where water adheres. For this reason, when PM adheres to the electrode 5 and the detected current increases, the electrode 5 is regenerated. Here, since the conditions for water to adhere to the electrode 5 are limited, it is considered that PM adheres to the electrode 5 when the detected current increases when this condition is not satisfied. Therefore, it is possible to distinguish between the case where water is attached to the electrode 5 and the case where PM is attached.

  FIG. 5 is a flowchart showing a control flow of the applied voltage according to the present embodiment. This routine is repeatedly executed by the control device 7 every predetermined time. Moreover, the same reference numerals are given to steps in which the same processing as the flow shown in the embodiment 1-3 is performed, and the description thereof is omitted.

  In step S401, it is estimated whether a condition for water to reach the electrode 5 is satisfied. For example, when condensed water exists in the exhaust passage 2 and the accelerator opening increases and the amount of exhaust gas increases, the condensed water adhering to the wall surface of the exhaust passage 2 scatters and the electrode 5 adheres. Thus, it is presumed that water reaches the electrode 5 when both the condition that the condensed water exists and the condition that the condensed water reaches the electrode 5 are established. Whether or not condensed water exists in the exhaust passage 2 can be estimated in the same manner as in step S106. Whether or not water reaches the electrode 5 is estimated based on the intake air amount detected by the air flow meter 74, for example. For example, it is determined that water reaches the electrode 5 when the intake air amount is equal to or greater than a threshold value. In this step, the amount of water adhering to the electrode 5 may be estimated. This amount can be estimated by a known technique based on the operating state of the internal combustion engine. For example, it may be assumed that water of droplets present in the exhaust adheres to the electrode 5 at a predetermined rate.

  In step S402, it is determined whether or not it is estimated in step S401 that the condition for water to reach the electrode 5 is satisfied. In this step, it may be determined whether the amount of water adhering to the electrode 5 is equal to or greater than a threshold value. This threshold is the amount of water adhering to the detection current at a predetermined value A. Here, since the detected current is determined to be equal to or larger than the predetermined value A in step S108, it is considered that either water or PM is attached to the electrode 5. And when it is estimated that the conditions for water to reach the electrode 5 are established, it is considered that the detected current is increased due to water adhering to the electrode 5. Therefore, when a positive determination is made in step S402, the process proceeds to step S301, and the applied voltage is reduced. On the other hand, if a negative determination is made in step S402, it is considered that PM has adhered to the electrode 5, so the process proceeds to step S403, where the electrode 5 is regenerated.

  Here, the regeneration of the electrode 5 is a process for removing deposits such as PM adhering to the electrode 5 including the insulator portion 51. For example, by short-circuiting the electrode 5, the temperature of the electrode 5 is raised and the deposits are removed by burning or evaporation. In order to oxidize PM quickly, it is better that the oxygen concentration in the exhaust gas is high. Therefore, the oxygen concentration in the exhaust gas may be increased before the electrode 5 is short-circuited or when the electrode 5 is short-circuited. In order to increase the oxygen concentration in the exhaust gas, for example, in a hybrid vehicle including an internal combustion engine and a motor as a vehicle drive source, the crankshaft of the internal combustion engine may be rotated by the motor without supplying fuel to the internal combustion engine. Good. Thereby, since air can be discharged | emitted from an internal combustion engine, the oxygen concentration in exhaust_gas | exhaustion can be raised. Further, by temporarily increasing the engine speed before stopping the internal combustion engine and stopping the fuel supply when the engine speed is high, air can be discharged into the exhaust passage. Then, the electrode 5 may be short-circuited when the internal combustion engine stops thereafter. Further, at the time of fuel cut during the deceleration operation, the oxygen concentration in the exhaust gas becomes high. Therefore, the electrode 5 may be short-circuited at this time.

  As described above, according to this embodiment, it is possible to distinguish between the case where PM is attached to the electrode 5 and the case where water is attached. When PM adheres to the electrode 5, regeneration of the electrode 5 is performed, so that excessive current can be prevented from passing and aggregation of PM can be promoted.

DESCRIPTION OF SYMBOLS 1 Particulate matter processing apparatus 2 Exhaust passage 3 Housing 4 Insulation part 5 Electrode 6 Power supply 7 Control apparatus 8 Battery 9 Detection apparatus 21 Flange 31 Flange 51 Insulator part 52 Power supply side electric wire 53 Ground side electric wire 71 Accelerator opening degree sensor 72 Crank position sensor 73 Engine temperature sensor 74 Air flow meter 75 Outside air temperature sensor 76 Exhaust passage temperature sensor

Claims (5)

An electrode provided in an exhaust passage of the internal combustion engine;
A power source connected to the electrode for applying a voltage;
A detection device for detecting a current through the electrode;
When the current detected by the detection device is equal to or greater than a predetermined value, an applied voltage reduction device that reduces the voltage applied from the power source to the electrode than when the current is less than a predetermined value;
A particulate matter processing apparatus comprising:   2. The particulate matter processing device according to claim 1, wherein the applied voltage reduction device stops the application of voltage to the electrode when the current detected by the detection device is equal to or greater than the predetermined value. An electrical resistance calculation device that calculates electrical resistance based on a current detected by the detection device;
A water removal determination device that determines that water has been removed from the electrode when the electrical resistance calculated by the electrical resistance calculation device is equal to or greater than a predetermined value;
The particulate matter processing apparatus according to claim 1, comprising: An estimation device for estimating an amount of water evaporated from the electrode based on an operating state of the internal combustion engine;
A water removal determination device that determines that water has been removed from the electrode when the amount of water estimated by the estimation device exceeds a predetermined value;
The particulate matter processing apparatus according to claim 1, comprising: A processing section provided in the exhaust passage and provided with the electrode;
An insulating part for insulating electricity between the processing part and the exhaust passage;
A grounding unit for grounding the processing unit;
A pulse current determination device for determining whether or not a pulse current is generated in the current detected by the detection device;
With
The detection device detects a current at the grounding unit,
When the current detected by the detection device is less than the predetermined value, the voltage applied to the electrode is increased until the pulse current determination device determines that a pulse current has been generated, and the pulse current determination device A pulse current suppression device that adjusts the voltage applied to the electrode to be lower than the voltage generated by the pulse current by reducing the voltage applied to the electrode when it is determined that a pulse current is generated by the method. The particulate matter processing apparatus according to any one of 1 to 4.

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