JP6506600B2 - Particle detection system - Google Patents

Description

  The present invention relates to a particulate matter detection system for detecting particulates in a gas to be measured by attaching a particulate matter sensor to a vent pipe through which the gas to be measured containing particulates flows.

  In internal combustion engines (for example, diesel engines), the exhaust gas may contain particulates such as soot. Exhaust gas containing such particulates is purified by collecting the particulates with a filter. Further, it is also practiced to burn and remove particulates accumulated in the filter by raising the temperature of the filter as necessary. However, if a failure such as breakage of the filter occurs, the unpurified exhaust gas is directly discharged downstream of the filter. Therefore, in order to directly measure the amount of particulates in the exhaust gas or detect a defect in the filter, a particulate detection system capable of detecting the amount of particulates in the exhaust gas is required.

  As such a particulate detection system, for example, as disclosed in Patent Document 1, a second discharge electrode that causes a corona discharge between a first discharge electrode, an insulator, and the first discharge electrode A particulate sensor having a second discharge electrode which is held by the insulator and a part of the second discharge electrode is exposed (projected) from the insulator; and a control device for controlling the particulate sensor What is known is provided with. In this particulate matter detection system, the first discharge is controlled by the control device while the particulate matter sensor is attached to a vent pipe (for example, an exhaust pipe) through which a gas to be measured (for example, exhaust gas) containing particulates flows. By applying a first voltage between the electrode and the second discharge electrode, the voltage between the first discharge electrode and the second discharge electrode (a portion of the second discharge electrode exposed from the insulator) Corona discharge is generated to generate ions around the second discharge electrode, and the ions are used to detect the fine particles in the gas to be measured.

JP, 2014-10099, A

  By the way, when the temperature of the gas to be measured which reaches the particulate sensor reaches a high temperature equal to or higher than a predetermined first temperature (for example, 600 ° C.), the insulation resistance between the first discharge electrode and the second discharge electrode is greatly reduced. In this state, when a first voltage is applied between the first discharge electrode and the second discharge electrode, between the first discharge electrode (or a member having the same potential as the first discharge electrode) and the second discharge electrode, Not corona discharge but spark discharge may occur. When such a spark discharge occurs, there is a possibility that a defect may occur in the particle detection system.

  Further, under such a high temperature environment, the insulation resistance of the surface of the insulator to which a part of the second discharge electrode is exposed (projected) is also greatly reduced, so that the above-mentioned spark discharge can In some cases, the second discharge electrode may be generated from the portion exposed from the insulator) through the surface of the insulator (by creeping the surface of the insulator). When such a spark discharge occurs, a mark of discharge remains on the surface of the insulator (pathway discharge path), and thereafter, the temperature of the gas to be measured which reaches the particulate sensor is a high temperature higher than the first temperature (for example, 600 ° C.) Even in the case where it does not become, creeping discharge through this discharge mark tends to be generated, and there is a possibility that the above-mentioned corona discharge can not be generated properly. For this reason, there is a possibility that the particulates in the gas to be measured can not be properly detected.

  The present invention has been made in view of the present situation, and the first discharge electrode (or the same as the first discharge electrode) is obtained even when the temperature of the measurement gas reaching the particulate sensor reaches a high temperature equal to or higher than the first temperature. An object of the present invention is to provide a particulate matter detection system capable of making it difficult to cause spark discharge (including spark discharge via the surface of an insulator) between a member of potential and the second discharge electrode.

(1) A second discharge electrode that causes a corona discharge to occur between the first discharge electrode, the insulator, and the first discharge electrode, wherein the second discharge electrode is held by the insulator and is a part of the second discharge electrode A particulate sensor having a second discharge electrode exposed from the insulator, and a control device for controlling the particulate sensor, wherein the particulate sensor is attached to a vent pipe through which a gas containing particulates flows In the state, by applying the first voltage between the first discharge electrode and the second discharge electrode under the control of the control device, the corona discharge is generated to cause ions around the second discharge electrode. In the particulate matter detection system which generates the particulate matter and detects the particulates in the gas to be measured using the ions, the control device generates a corona discharge between the first discharge electrode and the second discharge electrode. To make it A discharge voltage output unit that outputs a first voltage applied between the first discharge electrode and the second discharge electrode, and a prediction condition that can predict that the temperature of the gas to be measured that reaches the particle sensor will be the first temperature or more And a determination unit that determines at least one of whether the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature. The discharge voltage output unit when at least one of the judgment that the prediction condition is satisfied and the temperature of the gas to be measured which has reached the particle sensor is equal to or higher than the first temperature is determined It is preferable that the particle detection system includes a voltage reduction instruction unit that instructs to reduce the voltage output from the discharge voltage output unit to a second voltage lower than the first voltage .

The particle detection system described above is a second discharge electrode that causes a corona discharge to occur between the first discharge electrode, the insulator, and the first discharge electrode, the second discharge electrode being held by the insulator And a control unit configured to control the particulate sensor, and a second discharge electrode having a part of the electrode exposed from the insulator.
This particulate matter detection system applies a first voltage between the first discharge electrode and the second discharge electrode by the control of the control device in a state where the particulate matter sensor is attached to the vent pipe through which the gas to be measured containing the particulates flows. As a result, corona discharge is generated between the first discharge electrode and the second discharge electrode (the part of the second discharge electrode exposed from the insulator) to generate ions around the second discharge electrode. Particulates in the gas to be measured are detected using the ions.

  More specifically, for example, with the vent pipe as the ground potential and the first discharge electrode as the first potential different from the ground potential, the second potential (a positive potential higher than the first potential) is applied to the second discharge electrode. By applying the voltage, a first voltage is applied between the first discharge electrode and the second discharge electrode. Thereby, a corona discharge is generated between the first discharge electrode and the second discharge electrode, and corona (a portion of the second discharge electrode exposed from the insulator) as a positive electrode (corona) Generate a positive needle corona). Thereby, gas molecules in the atmosphere (air) forming the atmosphere are ionized to generate ions (cations) around the second discharge electrode. Then, ions (positive ions) generated around the second discharge electrode by the corona discharge are attached to the particles contained in the gas to be measured taken inside the particle sensor to generate charged charged particles. The amount of particulates in the gas to be measured is detected using a signal current that flows according to the amount of charged particulates between the first potential and the ground potential.

  In such a particulate detection system, as described above, when the temperature of the measurement gas reaching (in contact with) the particulate sensor reaches a high temperature equal to or higher than the first temperature (eg, 600 ° C.), the first discharge electrode (or the first There is a possibility that spark discharge rather than corona discharge may be generated between the second electrode and the second discharge electrode).

  On the other hand, in the particle detection system described above, whether or not a prediction condition that can predict that the temperature of the measurement gas that reaches (contacts) the particle sensor reaches the first temperature (for example, 600 ° C.) Determine if Alternatively, the determination unit determines whether the temperature of the gas to be measured that has reached (contacted) the particulate sensor is equal to or higher than a first temperature (eg, 600 ° C.).

  Furthermore, when it is determined in the determination unit that a prediction condition that can predict that the temperature of the measurement gas reaching (in contact with) the particle sensor reaches or exceeds the first temperature (eg, 600 ° C.) holds, the voltage reduction instruction unit The discharge voltage output unit is instructed to reduce the voltage output from the discharge voltage output unit to a second voltage lower than the first voltage (normal discharge voltage). Alternatively, when it is determined in the determination unit that the temperature of the gas to be measured that has reached (contacted) the particulate sensor is equal to or higher than the first temperature, the voltage reduction instruction unit outputs the discharge voltage output unit to the discharge voltage output unit. , And instructs to reduce the output voltage to a second voltage lower than the first voltage (normal discharge voltage).

  As a result, when the temperature of the gas to be measured which reaches the particulate sensor reaches a high temperature equal to or higher than the first temperature, the voltage applied between the first discharge electrode and the second discharge electrode is reduced, and the first discharge electrode A spark discharge (including a spark discharge via the surface of the insulator) can be less likely to occur between (or a member having the same potential as the first discharge electrode) and the second discharge electrode.

  The first temperature is the same as that of the first discharge electrode (or the first discharge electrode) when the first voltage is applied between the first discharge electrode and the second discharge electrode in the particle detection system described above. The temperature is selected from a temperature range in which spark discharge (including spark discharge via the insulator surface) can occur between the member and the second discharge electrode. The first temperature is preferably, for example, the lower limit value of the above temperature range. In the above-described temperature range, for example, in the particle detection system described above, the temperature of the gas to be measured that reaches the particle sensor is made different to various temperatures, and the first voltage is set between the first discharge electrode and the second discharge electrode. Can be grasped by conducting a test of applying.

  In addition, as the “predicting condition that can be predicted that the temperature of the measurement gas reaching the particulate sensor becomes equal to or higher than the first temperature”, for example, the exhaust purification filter is disposed upstream of the particulate sensor in the exhaust pipe which is a ventilating pipe. In the case where the exhaust gas purification device (DPF) provided inside is provided, "the exhaust gas purification filter is being regenerated" may be mentioned. When the filter regeneration processing is performed to burn the carbon particles collected by the exhaust purification filter and regenerate the exhaust purification filter, the temperature of the exhaust gas (gas to be measured) at the outlet of the exhaust purification device (exhaust purification filter) is , 600 ° C or more. For this reason, it can be predicted that the temperature of the exhaust gas (measured gas) reaching the particulate matter sensor becomes equal to or higher than the first temperature (for example, 600 ° C.). Therefore, for example, the determination unit determines whether the prediction condition is satisfied based on whether a signal indicating that the exhaust gas purification filter is being regenerated is received from the internal combustion engine control unit (ECU) or the like. Can.

  When the vent pipe on the upstream side of the particle sensor includes a temperature sensor for detecting the temperature of the measurement gas, the detection temperature of the measurement gas detected by the temperature sensor is the first temperature (for example, 600 ° C. When it becomes above, it can be predicted that the temperature of the gas to be measured which reaches the particulate sensor will be equal to or higher than the first temperature (for example, 600 ° C.). For this reason, in this case, it can be set as a prediction condition that "the detection temperature which a temperature sensor detected is more than the 1st temperature (for example, 600 ° C)." Therefore, for example, the determination unit receives the detected temperature detected by the temperature sensor from the internal combustion engine control unit (ECU) or the like, and determines whether the detected temperature is equal to or higher than the first temperature. Can be determined.

  Also, when a particulate sensor is attached to the exhaust pipe of a vehicle having an internal combustion engine, the internal combustion engine is continuously operated at a high load and high speed for a predetermined period of time, for example, when climbing a long slope. Even when the gas is continuously discharged, the temperature of the exhaust gas (measured gas) reaching the particulate sensor becomes equal to or higher than the first temperature (for example, 600 ° C.). Therefore, when the operating condition of the internal combustion engine is high load and high rotation, and this continues for a predetermined time (for example, 5 seconds), the temperature of the exhaust gas (gas to be measured) reaching the particulate sensor is the first temperature (for example, 600) It can be predicted that the temperature is higher than ° C. Therefore, for example, based on the operating conditions of the internal combustion engine including the rotational speed and the accelerator opening degree of the internal combustion engine received from the ECU etc., the determination unit performs the operating condition of high load and high rotation for a predetermined time (for example 5 seconds). It can be determined whether or not the prediction condition is satisfied by determining whether or not it is indicated.

  In addition, the determination as to whether the temperature of the gas to be measured that has reached the particulate sensor is equal to or higher than the first temperature may be, for example, a temperature sensor provided in the particulate sensor (if the particulate sensor has a heating resistor, This can be achieved by determining whether the detected temperature (which may be used as a sensor) is equal to or higher than the first temperature.

  The second voltage also includes 0V. That is, in order to “decrease the voltage output in the discharge voltage output unit to the second voltage lower than the first voltage”, the voltage output in the discharge voltage output unit is set to 0 V (specifically, for example, It also includes that the discharge voltage output unit is in an output stop state, and the discharge voltage output unit does not output a voltage).

(2) Furthermore, in the particulate matter detection system described above, the ventilation pipe is an exhaust pipe through which exhaust gas of an internal combustion engine flows, the measurement gas is the exhaust gas, and the exhaust pipe is the An exhaust gas purification device having an exhaust gas purification filter inside is provided upstream of the particulate matter sensor, and the determination unit determines that the exhaust gas purification filter in the exhaust gas purification device determines whether the prediction condition is satisfied. It is determined whether the filter regeneration process for regenerating the exhaust gas purification filter by burning the collected carbon particles is being performed, and the voltage reduction instruction unit is determined that the filter regeneration process is being performed by the determination unit. In this case, it is preferable that the particle detection system instructs the discharge voltage output unit to reduce the voltage output from the discharge voltage output unit to the second voltage .

  In the particulate matter detection system described above, the filter regeneration process (the carbon particles collected by the exhaust gas purification filter are burned to regenerate the exhaust gas purification filter in the exhaust gas purification device in which the determination unit is positioned upstream of the particulate matter sensor It is determined whether the process is in progress. When the filter regeneration process is performed, the temperature of the exhaust gas (gas to be measured) at the outlet of the exhaust gas purification device (exhaust gas purification filter) becomes 600 ° C. or higher (for example, 700 to 900 ° C.). For this reason, the temperature of the exhaust gas (measurement gas) reaching the particulate matter sensor positioned downstream of this becomes equal to or higher than the first temperature (for example, 600 ° C.).

  Therefore, in the particle detection system described above, the voltage reduction instruction unit causes the discharge voltage output unit to output the voltage output from the discharge voltage output unit to the second voltage when the determination unit determines that the filter regeneration process is in progress. To reduce the

  Thereby, when the temperature of the gas to be measured which reaches the particulate sensor reaches a high temperature equal to or higher than the first temperature by the filter regeneration process, the voltage applied between the first discharge electrode and the second discharge electrode is reduced. The spark discharge (including the spark discharge via the surface of the insulator) can be less likely to occur between the first discharge electrode (or a member having the same potential as the first discharge electrode) and the second discharge electrode.

(3) Furthermore, in the particle detection system according to any one of the above, the second voltage is generated when the temperature of the gas to be measured that has reached the particle sensor becomes equal to or higher than the first temperature. It is preferable that the particulate matter detection system has a size in which spark discharge does not occur between the electrode and a member having the same potential as the first discharge electrode and the first discharge electrode .

  In the particle detection system described above, the second discharge electrode, the first discharge electrode, and the second discharge electrode in a state in which the temperature of the measurement gas that has reached the particle sensor reaches a first voltage at a second voltage. The magnitude is such that spark discharge does not occur between a member having the same potential as the first discharge electrode.

  Therefore, when it is determined in the determination unit that the prediction condition that can be predicted that the temperature of the gas to be measured that reaches the particulate sensor reaches the first temperature (for example, 600 ° C.) is satisfied, the voltage reduction instruction unit outputs the discharge voltage The second discharge electrode and the first discharge electrode (and the same in the state where the temperature of the gas to be measured which has reached the particle sensor becomes equal to or higher than the first temperature) An instruction is given to reduce the magnitude to a level (= second voltage) at which spark discharge does not occur between the potential members). Alternatively, when the determination unit determines that the temperature of the gas to be measured that has reached the particulate sensor is equal to or higher than the first temperature, the voltage reduction instruction unit outputs the voltage output from the discharge voltage output unit to the discharge voltage output unit. “The spark discharge occurs between the second discharge electrode and the first discharge electrode (and a member of the same potential) when the temperature of the gas to be measured that has reached the particulate sensor has reached the first temperature or higher. It is instructed to reduce to no magnitude (= second voltage).

  As a result, when the temperature of the gas to be measured that reaches the particulate sensor reaches a high temperature equal to or higher than the first temperature, the distance between the first discharge electrode (or a member having the same potential as the first discharge electrode) and the second discharge electrode Generation of spark discharge (including spark discharge via the surface of the insulator) can be suppressed.

(4) Further, in the particle detection system described above, the voltage reduction instruction unit is configured such that, in the determination unit, the prediction condition is satisfied, and the temperature of the measurement gas that has reached the particle sensor is the It is preferable that the particulate matter detection system instructs the discharge voltage output unit to stop the output of the discharge voltage output unit when at least one of the determination that the temperature is 1 temperature or more is made .

  In the particle detection system described above, at least one of the judgment that the prediction condition is satisfied and the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature is determined in the determination unit. The voltage reduction instructing unit instructs the discharge voltage output unit to stop the output of the discharge voltage output unit (that is, not to output the voltage from the discharge voltage output unit). That is, “the size is such that spark discharge does not occur between the second discharge electrode and the first discharge electrode when the temperature of the gas to be measured which has reached the particle sensor is equal to or higher than the first temperature” Set the voltage to 0V.

Thereby, when the temperature of the gas to be measured which reaches the particulate sensor reaches a high temperature equal to or higher than the first temperature, between the first discharge electrode (or a member having the same potential as the first discharge electrode) and the second discharge electrode It is possible to prevent the occurrence of spark discharge (including spark discharge via the insulator surface).
One aspect of the present invention is the particulate matter detection system according to (1), which is the particulate matter detection system according to (3) and the particulate matter detection system according to (4).
That is, one aspect of the present invention is a second discharge electrode that causes a corona discharge to occur between the first discharge electrode, the insulator, and the first discharge electrode, wherein the second discharge electrode is held by the insulator and the second discharge electrode is (2) A particulate pipe having a second discharge electrode in which a part of the discharge electrode is exposed from the insulator, and a control device for controlling the particulate sensor, and a vent pipe through which a gas containing particulates flows The corona discharge is generated by applying a first voltage between the first discharge electrode and the second discharge electrode under the control of the control device in a state where the particle sensor is mounted, thereby generating the corona discharge. In the particle detection system for generating ions around the discharge electrode and detecting the particles in the gas to be measured by using the ions, the control device comprises a combination of the first discharge electrode and the second discharge electrode. Between corona discharge A discharge voltage output unit for outputting a first voltage applied between the first discharge electrode and the second discharge electrode to generate the temperature, and a temperature of the gas to be measured that reaches the particle sensor is equal to or higher than the first temperature A determination unit that determines at least one of whether a prediction condition that can be predicted is satisfied and whether the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature And the determination unit determines that the prediction condition is satisfied and / or the temperature of the gas to be measured which has reached the particle sensor is equal to or higher than the first temperature. A voltage reduction instruction unit for instructing the discharge voltage output unit to reduce the voltage output from the discharge voltage output unit to a second voltage lower than the first voltage, the second voltage being the voltage In a state in which the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature, the distance between the second discharge electrode and a member having the same potential as the first discharge electrode and the first discharge electrode And the voltage reduction instruction unit has the determination unit satisfied the prediction condition in the determination unit, and the temperature of the gas to be measured that has reached the particle sensor is the first temperature or more. The particle detection system instructs the discharge voltage output unit to stop the output of the discharge voltage output unit when at least one of the determination is made.
Furthermore, it is preferable that it is said particle | grain detection system, Comprising: It is a particle | grain detection system of said (2).
That is, in the particulate detection system described above, the ventilation pipe is an exhaust pipe through which the exhaust gas of the internal combustion engine flows, the measurement gas is the exhaust gas, and the exhaust pipe is the particulate sensor The exhaust gas purification apparatus having an exhaust gas purification filter inside is also provided on the upstream side, and the determination unit is collected by the exhaust gas purification filter in the exhaust gas purification apparatus as a determination as to whether the prediction condition is satisfied. It is determined whether or not the filter regeneration process for regenerating the exhaust gas purification filter by burning out the carbon particles is being performed, and the voltage reduction instruction unit determines that the filter regeneration process is being performed by the determination unit. The particle detection system may instruct the discharge voltage output unit to stop the output of the discharge voltage output unit.

BRIEF DESCRIPTION OF THE DRAWINGS It is the schematic of the vehicle carrying the particle | grain detection system of embodiment. It is a longitudinal cross-sectional view of a particulate sensor which constitutes a particulate detection system of an embodiment. It is a disassembled perspective view of the particle sensor. 1 is a schematic view of a particle detection system according to an embodiment. It is a perspective view of a ceramic element which constitutes a particulate sensor. It is an exploded perspective view of the ceramic element. It is an explanatory view of a particulate matter detection system of an embodiment. It is a flowchart which shows the flow of the microparticles | fine-particles detection which concerns on embodiment. It is the schematic of the microparticles | fine-particles detection system which concerns on a 1st modification. It is a flowchart which shows the flow of the microparticles | fine-particles detection which concerns on a 1st modification. It is a figure explaining the particulate matter detection system concerning the 2nd modification.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a vehicle AM equipped with the particulate matter detection system 1 of the embodiment. FIG. 2 is a cross-sectional view of the particulate sensor 10 included in the particulate detection system 1 according to the embodiment. FIG. 3 is an exploded perspective view of the particulate sensor 10. FIG. 4 is a schematic view of the particle detection system 1 according to the embodiment. However, in FIG. 4, the control device 200 included in the particle detection system 1 is mainly illustrated, and only a part (electric wire 161 or the like) of the particle sensor 10 is illustrated. In FIG. 2, in the longitudinal direction GH of the particle sensor 10, the end side GS on the side where the gas intake pipe 25 is disposed (downward in FIG. 2) extends the electric wires 161 and 163 on the opposite side. The side (upper side in FIG. 2) is referred to as a proximal side GK.

  The particulate matter detection system 1 includes a particulate matter sensor 10 and a control device 200 as shown in FIG. In this particulate matter detection system 1, the particulate matter sensor 10 is mounted on an exhaust pipe EP (vent pipe) of an engine ENG (internal combustion engine) mounted on a vehicle AM, and exhaust gas EG (measured gas) flowing in the exhaust pipe EP ) To detect the amount of particulates S (such as wrinkles) in the The particle detection system 1 is connected to an engine control unit ECU (internal combustion engine control device) that controls the engine ENG through a CAN bus. Further, on the upstream side of the particulate matter sensor 10, an exhaust purification device DPF having an exhaust purification filter PF inside is provided.

  Next, the particle sensor 10 will be described in detail. The particulate sensor 10 is attached to a metal exhaust pipe EP set to a ground potential PVE (chassis GND of the vehicle AM) (see FIG. 2). Specifically, a gas intake pipe 25 which is a tip end portion of the inner metal fitting 20 of the particulate sensor 10 is disposed in the exhaust pipe EP through a mounting opening EPO provided in the exhaust pipe EP. Then, among the exhaust gas EG flowing in the exhaust pipe EP, the ion CP is made to adhere to the particulates S in the intake gas EGI taken into the gas intake pipe 25 from the gas intake port 65c to form charged microparticles SC. The gas is discharged to the exhaust pipe EP from the gas discharge port 60e together with the inflowing gas EGI (see FIG. 7).

The particulate sensor 10 includes an inner fitting 20 having a gas intake pipe 25, an outer fitting 70, a first insulating spacer 100, a second insulating spacer 110, a ceramic element 120, four electric wires 161, 163, 173, 175, etc. (See FIGS. 2 and 3).
Among these, the inner metal fitting 20 is connected to the control device 200 through inner outer conductors 161g1 and 163g1 of electric wires 161 and 163 described later, and is set to a first potential PV1 different from the ground potential PVE. The inner fitting 20 includes a metal shell 30, an inner cylinder 40, an inner fitting 50, and a gas intake pipe 25 (an inner protector 60 and an outer protector 65).

  The metal shell 30 is a cylindrical stainless steel member extending in the longitudinal direction GH. The metal shell 30 has an annular flange 31 that bulges outward in the radial direction. Inside the metal shell 30, a cup-shaped metal cup 33 is disposed. A hole is formed in the bottom of the metal cup 33, and a ceramic element 120 described later is inserted through the hole.

  Inside the metal shell 30, a cylindrical ceramic holder 34 made of alumina and a first powder formed by compressing talc powder around the ceramic element 120 sequentially from the tip side GS to the base end side GK A filling layer 35, a second powder filling layer 36, and a cylindrical ceramic sleeve 37 made of alumina are disposed. The ceramic holder 34 and the first powder filling layer 35 are located in the metal cup 33. Further, the crimped portion 30 kk on the most proximal side GK of the metal shell 30 is crimped radially inward, and presses the ceramic sleeve 37 against the distal end side GS via the crimp ring 38.

  The inner cylinder 40 is a cylindrical stainless steel member extending in the longitudinal direction GH. The tip end portion of the inner cylinder 40 is an annular flange portion 41 projecting radially outward. The inner cylinder 40 is externally fitted to the proximal end side portion 30k of the metal shell 30, and is laser-welded to the proximal end side portion 30k in a state where the flange portion 41 overlaps the flange portion 31.

  Inside the inner cylinder 40, an insulation holder 43, a first separator 44, and a second separator 45 are disposed in this order from the tip end side GS to the base end side GK. Among them, the insulating holder 43 is cylindrical and made of an insulator, and is in contact with the ceramic sleeve 37 from the proximal end GK. The ceramic element 120 is inserted into the insulating holder 43.

  The first separator 44 is made of an insulator and has an insertion hole 44c. The ceramic element 120 is inserted into the insertion hole 44c, and the tip end portion of the discharge potential terminal 46 is accommodated. In the insertion hole 44c, the discharge potential terminal 46 is in contact with a later-described discharge potential pad 135 (see FIGS. 5 and 6) of the ceramic element 120.

  On the other hand, the second separator 45 is made of an insulator, and has a first insertion hole 45c and a second insertion hole 45d. The base end side portion of the discharge potential terminal 46 accommodated in the first insertion hole 45c and the tip end portion of the discharge potential lead wire 162 described later are connected in the first insertion hole 45c.

  In addition to the element base end 120k of the ceramic element 120 being disposed in the second insertion hole 45d, the auxiliary potential terminal 47, the 2-1st heater terminal 48, and the 2-2nd heater terminal 49 are mutually insulated. Are housed in the Then, in the second insertion hole 45d, the auxiliary potential terminal 47 contacts the auxiliary potential pad 147 of the ceramic element 120, and the 2-1st heater terminal 48 contacts the 2-1st heater pad 156 of the ceramic element 120. The second 2-2 heater terminal 49 is in contact with the second 2-2 heater pad 158 of the ceramic element 120 (see FIGS. 2, 3, 5 and 6).

  Furthermore, in the second insertion hole 45d, tip portions of an auxiliary potential lead wire 164, a 2-1 heater lead wire 174, and a 2-2 heater lead wire 176, which will be described later, are respectively disposed. Then, in the second insertion hole 45d, the auxiliary potential terminal 47 and the auxiliary potential lead wire 164 are connected, the 2-1st heater terminal 48 and the 2-1st heater lead wire 174 are connected, and the 2-2nd heater terminal 49 and the 2-2 heater lead wire 176 are connected.

  The inner cylinder connection metal fitting 50 is a stainless steel member and is externally fitted to the base end 40k of the inner cylinder 40 while surrounding the base end side portion of the second separator 45, and the tip 50s of the inner cylinder connection metal fitting 50 is Laser welding is performed on the proximal end 40k of the inner cylinder 40. Four electric wires 161, 163, 173, and 175 are inserted through the inner cylinder connection fitting 50, respectively. Among these, inner outer conductors 161g1 and 163g1 of electric wires 161 and 163 of a triple coaxial cable described later are connected to the inner cylinder connection fitting 50.

  The gas intake pipe 25 is composed of an inner protector 60 (first discharge electrode) and an outer protector 65. The inner protector 60 is a bottomed cylindrical stainless steel member, and the outer protector 65 is a cylindrical stainless steel member. The outer protector 65 is disposed around the radial direction of the inner protector 60. The inner protector 60 and the outer protector 65 are externally fitted to the front end 30s of the metal shell 30, and laser welded to the front end 30s. The gas intake pipe 25 surrounds the tip end side portion of the ceramic element 120 projecting from the metal shell 30 to the tip end side GS from the outside in the radial direction, and protects the ceramic element 120 from water droplets and foreign matter, while the exhaust gas EG is ceramic It leads around the element 120.

  A plurality of rectangular gas inlets 65 c are formed at the tip end portion of the outer protector 65 for taking the exhaust gas EG flowing in the exhaust pipe EP into the inside of the outer protector 65. Further, in the inner protector 60, in order to further introduce the intake gas EGI taken into the outer protector 65 among the exhaust gas EG flowing in the exhaust pipe EP, to the inner end of the inner protector 60, A plurality of circular first inner introduction holes 60c are formed. In addition, a plurality of triangular second inner introduction holes 60d are also formed in the tip end portion of the inner protector 60. Furthermore, at the bottom of the inner protector 60, a circular gas outlet 60e for discharging the intake gas EGI to the exhaust pipe EP is formed. The tip portion 60s of the inner protector 60 including the gas discharge port 60e protrudes from the tip opening 65s of the outer protector 65 to the tip side GS.

  Here, the intake and exhaust of the exhaust gas EG to the inner protector 60 and the outer protector 65 when the particulate sensor 10 is used will be described with reference to FIG. In FIG. 7, the exhaust gas EG flows from the left to the right in the exhaust pipe EP. When the exhaust gas EG passes around the outer protector 65 and the inner protector 60, the flow velocity rises outside the gas outlet 60e of the inner protector 60, and a negative pressure is generated near the gas outlet 60e due to the venturi effect. .

  Then, the intake gas EGI taken into the inside protector 60 by this negative pressure is discharged from the gas discharge port 60e to the exhaust pipe EP. At the same time, exhaust gas EG around the gas inlet 65c of the outer protector 65 is taken into the outer protector 65 from the gas inlet 65c, and further, inside the inner protector 60 through the first inner introduction hole 60c of the inner protector 60. Incorporated into Then, the intake gas EGI in the inner protector 60 is discharged from the gas discharge port 60e. Therefore, as indicated by the broken line arrow, an air flow of the intake gas EGI flowing from the first inner introduction hole 60c on the proximal end GK toward the gas discharge port 60e on the distal end GS is generated in the inner protector 60.

  Next, the outer bracket 70 will be described. As shown in FIGS. 2 and 3, the outer fitting 70 is cylindrical and made of metal, and the radial circumference of the inner fitting 20 is surrounded by the inner fitting 20 at a distance from the inner fitting 20, and the exhaust pipe is set to the ground potential PVE. It is attached to the EP and is set to the ground potential PVE. The outer fitting 70 includes a mounting fitting 80 and an outer cylinder 90.

  The mounting bracket 80 is a cylindrical, stainless steel member extending in the longitudinal direction GH. The mounting bracket 80 is disposed around the radial direction of the front end side portion of the metal shell 30 and the inner cylinder 40 in the inner bracket 20 so as to be separated therefrom. The mounting bracket 80 has a flange portion 81 which bulges outward in the radial direction to form an outer hexagonal shape. In addition, inside the mounting bracket 80, a stepped portion 83 having a stepped shape is provided. Further, a male screw (not shown) used for fixing to the exhaust pipe EP is formed on the outer periphery of the distal end side 80s of the mounting bracket 80 on the distal end side GS than the flange portion 81. The particle sensor 10 is attached to a metal mounting boss BO separately fixed to the exhaust pipe EP by an external thread of the tip side portion 80s, and is fixed to the exhaust pipe EP via the mounting boss BO (see FIG. See Figure 2).

  A first insulating spacer 100 and a second insulating spacer 110, which will be described later, are disposed between the mounting bracket 80 and the inner bracket 20. The crimped portion 80 kk on the most proximal side GK of the mounting bracket 80 is crimped radially inward, and presses the second insulating spacer 110 to the distal end side GS via the wire packing 87.

  The outer cylinder 90 is a cylindrical member extending in the longitudinal direction GH, and is a stainless steel member. The distal end portion 90s of the outer cylinder 90 is externally fitted to the proximal end side 80k of the mounting bracket 80, and is laser-welded to the proximal end side 80k. An outer cylinder connection fitting 95 is disposed in the small diameter portion 91 located on the proximal end GK of the outer cylinder 90, and a fluororubber grommet 97 is disposed on the proximal end GK. Four electric wires 161, 163, 173, 175, which will be described later, are respectively inserted into the outer cylinder connection fitting 95 and the grommet 97. Among these, outer outer conductors 161g2 and 163g2 of electric wires 161 and 163 of a triple coaxial cable to be described later are connected to the outer cylinder connection fitting 95, respectively. The outer cylinder connection fitting 95 is reduced in diameter radially inward by caulking together with the small diameter portion 91 of the outer cylinder 90, whereby the outer cylinder connection fitting 95 and the grommet 97 are fixed in the small diameter portion 91 of the outer cylinder 90. ing.

  Next, the first insulating spacer 100 will be described. The first insulating spacer 100 is made of alumina and has a cylindrical shape extending in the longitudinal direction GH (see FIGS. 2 and 3). The first insulating spacer 100 is interposed between the inner fitting 20 and the outer fitting 70 to electrically insulate the two. Specifically, it is disposed between the front end side portions of the metal shell 30 and the inner cylinder 40 of the inner metal fitting 20 and the mounting metal 80 of the outer metal fitting 70. The first insulating spacer 100 has a small-diameter spacer tip side 101 located on the distal side GS, a large-size spacer proximal side 103 located on the proximal side GK, and a spacer middle portion connecting these And 102.

  The spacer middle portion 102 has an outer step surface (spacer contact surface) 102s facing the distal end side GS and an inner step surface 102k facing the proximal end GK (see FIG. 3). The outer step surface 102s and the inner step surface 102k both form an annular shape extending in the circumferential direction of the first insulating spacer 100. The outer stepped surface 102s abuts on the stepped portion 83 of the mounting bracket 80 from the proximal end GK over the entire circumference. On the other hand, the flange portion 31 of the metal shell 30 is in contact with the inner step surface 102k from the proximal end GK.

  Next, the second insulating spacer 110 will be described. The second insulating spacer 110 is a tubular member made of alumina extending in the longitudinal direction GH (see FIGS. 2 and 3). The second insulating spacer 110 is interposed between the inner fitting 20 and the outer fitting 70 to electrically insulate the two. Specifically, the second insulating spacer 110 is disposed between the tip end portion of the inner cylinder 40 of the inner fitting 20 and the mounting fitting 80 of the outer fitting 70. The second insulating spacer 110 includes a distal end side 111 located on the distal end side GS and a proximal end side 113 located on the proximal end GK.

  Among them, the distal end side portion 111 is thinner and thinner than the proximal end side portion 113. The distal end side portion 111 is disposed between the spacer proximal end portion 103 of the first insulating spacer 100 and the inner cylinder 40. On the other hand, the base end side portion 113 is located on the base end side GK relative to the spacer base end side portion 103 of the first insulating spacer 100, and is disposed between the mounting bracket 80 and the inner cylinder 40.

  As described above, the crimped portion 80 kk of the mounting bracket 80 presses the second insulating spacer 110 against the leading end side GS via the wire packing 87. As a result, the tip side portion 111 of the second insulating spacer 110 presses the flange portion 41 of the inner cylinder 40 and the flange portion 31 of the metal shell 30 against the tip side GS. Further, the flanges 41 and 31 press the spacer middle portion 102 of the first insulating spacer 100 to the tip end side GS, and the spacer middle portion 102 engages with the step portion 83 of the mounting bracket 80. Thus, the first insulating spacer 100 and the second insulating spacer 110 are fixed between the inner fitting 20 (the tip end portion of the main fitting 30 and the inner cylinder 40) and the outer fitting 70 (mounting fitting 80).

  Next, the ceramic element 120 will be described. The ceramic element 120 has a plate-like insulating ceramic base 121 made of alumina extending in the longitudinal direction GH (see FIGS. 5 and 6). In the ceramic base 121, a part of the discharge electrode body 130 (second discharge electrode), the auxiliary electrode body 140 and the heater 150 for the element are embedded, and these are integrally sintered with the ceramic base 121.

  Specifically, the ceramic substrate 121 is formed by laminating three ceramic layers 122, 123 and 124 made of alumina derived from an alumina green sheet, and two insulating coatings made of alumina formed by printing between these layers. Layers 125 and 126 intervene respectively. Among them, the ceramic layer 122 and the insulating covering layer 125 are shorter in the longitudinal direction GH at the distal end side GS and the proximal end side GK than the ceramic layers 123 and 124 and the insulating covering layer 126, respectively. The discharge electrode body 130 is disposed between the insulating covering layer 125 and the ceramic layer 123. Further, the auxiliary electrode body 140 is disposed between the ceramic layer 123 and the insulating covering layer 126, and the element heater 150 is disposed between the insulating covering layer 126 and the ceramic layer 124.

The discharge electrode body 130 (second discharge electrode) has a form extending in the longitudinal direction GH, and a needle-like needle-like electrode portion 131 located on the distal end side GS and a discharge potential pad located on the proximal end GK It consists of 135 and the lead part 133 which ties between these. The needle-like electrode portion 131 is made of a platinum wire. On the other hand, the lead portion 133 and the discharge potential pad 135 are made of pattern printed tungsten. Of the discharge electrode body 130, the base end side portion 131k of the needle-like electrode portion 131 and the whole of the lead portion 133 are embedded in the ceramic base 121. Thereby, the discharge electrode body 130 is hold | maintained at the ceramic base 121 (insulator) (refer FIG. 5).
On the other hand, the tip side portion 131s of the needle-like electrode portion 131 is exposed (projected) from the ceramic base 121 at the tip side GS of the ceramic base 121 with respect to the ceramic layer 122 (see FIG. 5). Further, the discharge potential pad 135 is exposed on the proximal side GK of the ceramic base 121 relative to the ceramic layer 122. As described above, the discharge potential terminal 46 contacts the discharge potential pad 135 in the insertion hole 44 c of the first separator 44. Thus, part of the discharge electrode body 130 (the tip side portion 131s of the needle-like electrode portion 131 and the discharge potential pad 135) is exposed from the ceramic base 121.

  The auxiliary electrode body 140 has a form extending in the longitudinal direction GH, is formed by pattern printing, and is entirely embedded in the ceramic substrate 121. The auxiliary electrode body 140 is located on the distal end side GS, and includes a rectangular auxiliary electrode portion 141 and a lead portion 143 connected to the auxiliary electrode portion 141 and extending to the proximal end GK. The base end 143 k of the lead portion 143 is connected to the conduction pattern 145 formed on one main surface 124 a of the ceramic layer 124 through the through hole 126 c of the insulating covering layer 126. Further, the conductive pattern 145 is connected to the auxiliary potential pad 147 formed on the other main surface 124 b of the ceramic layer 124 through the through-hole conductor 146 formed through the ceramic layer 124. As described above, the auxiliary potential terminal 47 contacts the auxiliary potential pad 147 in the second insertion hole 45 d of the second separator 45.

  The element heater 150 is formed by pattern printing, and the whole is embedded in the ceramic base 121. The element heater 150 is located on the front end side GS, and has a heating resistor 151 for heating the ceramic element 120, and a pair of heater lead portions 152 and 153 connected to both ends of the heating resistor 151 and extending to the base end GK. It consists of The base end 152 k of one heater lead portion 152 is on the 2-1st heater pad 156 formed on the other main surface 124 b of the ceramic layer 124 through the through-hole conductor 155 formed through the ceramic layer 124. Connected As described above, the (2-1) th heater terminal 48 contacts the (2-1) th heater pad 156 in the second insertion hole 45d of the second separator 45. The base end 153 k of the other heater lead portion 153 is a 2-2nd heater pad formed on the other main surface 124 b of the ceramic layer 124 through the through-hole conductor 157 formed in the ceramic layer 124. Connected to 158. As described above, the second heater terminal 49 is in contact with the second heater pad 158 in the second insertion hole 45 d of the second separator 45.

Next, the electric wires 161, 163, 173, and 175 will be described. Of these four electric wires, two electric wires 161 and 163 are triple coaxial cables (triaxial cables), and the remaining two electric wires 173 and 175 are small diameter single core insulated electric wires.
Among them, the electric wire 161 has a discharge potential lead wire 162 as a core wire (center conductor), and the discharge potential lead wire 162 is a discharge potential terminal 46 in the first insertion hole 45 c of the second separator 45 as described above. Connected to Further, the electric wire 163 has an auxiliary potential lead wire 164 as a core wire (central conductor), and the auxiliary potential lead wire 164 is connected to the auxiliary potential terminal 47 in the second insertion hole 45 d of the second separator 45. . Further, among the coaxial double outer conductors of the electric wires 161 and 163, the inner outer conductors 161g1 and 163g1 are connected to the inner cylinder connection fitting 50 of the inner fitting 20, and are set to the first potential PV1. On the other hand, the outer external conductors 161g2 and 163g2 are connected to the outer cylinder connection fitting 95 which is electrically connected to the outer fitting 70, and set to the ground potential PVE.

  Moreover, the electric wire 173 has the 2-1st heater lead wire 174 as a core wire. The second-first heater lead wire 174 is connected to the second-first heater terminal 48 in the second insertion hole 45 d of the second separator 45. Moreover, the electric wire 175 has a 2nd-2 heater lead wire 176 as a core wire. The second 2-2 heater lead wire 176 is connected to the second 2-2 heater terminal 49 in the second insertion hole 45 d of the second separator 45.

  Next, the control device 200 will be described. As shown in FIG. 4, the control device 200 is connected to the electric wires 161, 163, 173, and 175 of the particle sensor 10, and controls the particle sensor 10. Specifically, the particle sensor 10 is driven, and a signal current Is described later is detected. The control device 200 is driven by an external battery BT through a power supply wiring BC. Further, the control device 200 can communicate with an engine control unit ECU that controls an internal combustion engine via a communication line CC.

  The control device 200 is configured by electronic circuit components such as a microcomputer, and includes a voltage output unit 250 and a measurement control unit 280. Among these, the voltage output unit 250 includes a discharge voltage output unit 210 and an auxiliary voltage output unit 240. In addition, the measurement control unit 280 includes a determination unit 220, a voltage reduction instruction unit 230, a particle detection unit 260, and a heater energization unit 270.

  The discharge voltage output unit 210 generates a discharge voltage (first voltage) for generating a corona discharge between the inner protector 60 (first discharge electrode) and the discharge electrode body 130 (second discharge electrode) of the ceramic element 120. Output. Specifically, the discharge voltage output unit 210 applies a second potential PV2 (a positive potential higher than the first potential PV1) to the discharge electrode body 130 (second discharge electrode). Thus, a first voltage is applied between the inner protector 60 (first discharge electrode) and the discharge electrode body 130 (second discharge electrode), which are set to the first potential PV1, and the inner protector 60 and the discharge electrode body 130 are thus obtained. And generate a corona around the discharge electrode body 130 (second discharge electrode).

  The auxiliary voltage output unit 240 applies an auxiliary electrode potential PV3 to the auxiliary electrode body 140. The auxiliary electrode potential PV3 is a positive direct current high potential with respect to the first potential PV1, but is lower than the peak potential of the second potential PV2.

  Determination unit 220 determines whether or not a prediction condition that can predict that the temperature of exhaust gas EG (measured gas) reaching (contacting) particulate sensor 10 becomes equal to or higher than the first temperature (600 ° C. in this embodiment) is satisfied. Make a decision. Specifically, determination unit 220 outputs a signal during regeneration SR indicating that the filter regeneration process of exhaust purification device DPF is in progress, from the ECU, via communication line CC (specifically, CAN bus) During reproduction, a signal SR is received from the ECU (see FIG. 4).

  By the way, during the filter regeneration processing for regenerating the exhaust gas purification filter PF of the exhaust gas purification device DPF, the adhered carbon particles are burned and the exhaust gas EG of 600 ° C. or more (for example, 700 ° C. to 900 ° C.) is discharged. That is, during the filter regeneration process, the high temperature exhaust gas EG continues to be discharged from the exhaust gas purification device DPF. Therefore, during the filter regeneration process, it can be predicted that the temperature of the exhaust gas EG (measurement gas) reaching the particulate sensor 10 becomes equal to or higher than the first temperature (600 ° C.). Therefore, the determination unit 220 determines whether the prediction condition is satisfied depending on whether the signal SR during reproduction is received.

  When it is determined in the determination unit 220 that the voltage reduction instruction unit 230 has received the signal SR during regeneration, the voltage reduction instruction unit 230 outputs the first voltage (= second voltage) to the discharge voltage output unit 210 to the discharge voltage output unit 210. It is instructed to reduce to the second voltage lower than the potential PV2-the first potential PV1). In the present embodiment, the discharge electrode body 130 and the inner protector 60 (or the second electrode 60 or the inner protector 60 in a state where the temperature of the exhaust gas EG that has reached the particulate sensor 10 becomes higher than the first temperature (600.degree. C.). It is set so that spark discharge does not occur between members of the same potential. Specifically, the second voltage is set to 0V. Therefore, the voltage reduction instructing unit 230 instructs the discharge voltage output unit 210 to set the output stop state (do not output the voltage).

The particle detection unit 260 detects a signal current Is flowing between a first potential PV1 described later and the ground potential PVE. Then, the particle detector 260 detects the amount of particles S contained in the exhaust gas EG based on the magnitude of the signal current Is.
Further, the heater energizing unit 270 energizes the element heater 150 of the ceramic element 120 by PWM control to cause the element heater 150 to generate heat.

Next, the electrical function and operation of the particle detection system 1 will be described.
The discharge electrode body 130 of the ceramic element 120 is connected to the control device 200 (discharge voltage output unit 210) via the discharge potential lead wire 162 of the electric wire 161, and is set to the second potential PV2 (FIG. 4 to FIG. 6). On the other hand, the auxiliary electrode body 140 of the ceramic element 120 is connected to the control device 200 (auxiliary voltage output unit 240) through the auxiliary potential lead wire 164 of the electric wire 163, and is set to the auxiliary electrode potential PV3. Furthermore, the inner fitting 20 is connected to the control device 200 via the inner outer conductors 161g1 and 163g1 of the electric wires 161 and 163, and is set to the first potential PV1 (see FIGS. 2 to 4). In addition, the outer fitting 70 is connected to the control device 200 through the outer outer conductors 161g2 and 163g2 of the electric wires 161 and 163, and is set to the ground potential PVE.

  Here, the discharge potential lead wire 162 of the electric wire 161, the discharge potential terminal 46, and the discharge potential pad from the discharge voltage output portion 210 of the control device 200 to the needle electrode portion 131 of the discharge electrode body 130 (second discharge electrode) A second high potential (e.g., 1-2 kV) second potential PV2 is applied through 135. Then, a first voltage is applied between the needle-like tip end portion 131ss (second discharge electrode) of the needle-like electrode portion 131 and the inner protector 60 (first discharge electrode) set to the first potential PV1. A corona discharge is generated between the rod-shaped tip portion 131ss and the inner protector 60, and ions CP (cations) are generated around the needle-shaped tip portion 131ss (see FIG. 7).

  As described above, the exhaust gas EG is introduced into the inner protector 60 by the action of the gas intake pipe 25, and in the vicinity of the ceramic element 120, the air flow of the intake gas EGI from the proximal end GK toward the distal end GS It is happening. Therefore, the generated ions CP adhere to the particulates S in the intake gas EGI. Thereby, the fine particles S become charged fine particles SC charged positively, and flow toward the gas discharge port 60e together with the intake gas EGI, and are discharged to the exhaust pipe EP (see FIG. 7).

  On the other hand, in the auxiliary electrode portion 141 of the auxiliary electrode body 140, a predetermined potential (the auxiliary potential lead wire 164 of the electric wire 163, the auxiliary potential terminal 47, and the auxiliary potential pad 147) For example, an auxiliary electrode potential PV3 of 100 to 200 V (positive direct current potential) is applied. As a result, among the generated ions CP, the floating ions CPF that did not adhere to the particulates S are given a repulsive force directed from the auxiliary electrode portion 141 toward the radially outer inner protector 60 (collection electrode). And floating ion CPF is made to adhere to each part of a collection pole (inner protector 60), and collection is assisted (refer to Drawing 7). Thus, the floating ion CPF can be reliably collected, and even the floating ion CPF can be prevented from being discharged from the gas outlet 60e.

Then, in the particle detection system 1, the particle detection unit 260 detects a signal (signal current Is) corresponding to the charge amount of the discharged ions CPH attached to the charged particles SC discharged from the gas discharge port 60 e. The signal current Is flows between the first potential PV1 (potential of the inner protector 60 etc.) and the ground potential PVE (potential of the exhaust pipe EP etc). Thereby, the amount (concentration) of the particulates S contained in the exhaust gas EG can be detected.
As described above, in the present embodiment, the ion CP generated by corona discharge is caused to adhere to the particulates S contained in the exhaust gas EG taken into the inside of the gas intake pipe 25 to generate the charged particulates SC, The amount of particulates S in the exhaust gas EG is detected using the signal current Is flowing between the first potential PV1 and the ground potential PVE according to the amount of the charged particulates SC.

  Furthermore, the particulate sensor 10 has a heater 150 for the element on the ceramic element 120. The 2-1st heater pad 156 of the element heater 150 is connected to the heater energization unit 270 of the control device 200 via the 2-1st heater terminal 48 and the 2-1nd heater lead wire 174 of the electric wire 173. There is. Further, the 2-2nd heater pad 158 of the element heater 150 is connected to the heater energization unit 270 of the control device 200 via the 2-2nd heater terminal 49 and the 2-2nd heater lead wire 176 of the electric wire 175. ing.

  For this reason, when a predetermined heater energization voltage is applied between the 2-1 heater pad 156 and the 2-2 heater pad 158 from the heater energization unit 270, the heating resistor 151 of the element heater 150 generates heat due to energization. Do. As a result, the ceramic element 120 can be heated to remove foreign matter such as water droplets and wrinkles attached to the ceramic element 120, so that the insulation of the ceramic element 120 can be recovered or maintained.

  By the way, the exhaust gas purification device DPF is provided on the upstream side of the exhaust pipe EP than the particulate matter sensor 10 (see FIG. 1). The exhaust purification device DPF collects carbon particles in the exhaust gas EG by an exhaust purification filter PF provided in the exhaust purification device DPF. As a result, carbon particles are removed from the exhaust gas EG that has passed through the exhaust gas purification filter PF. Then, the exhaust purification device DPF oxidizes and burns the carbon particles collected by the exhaust purification filter PF to regenerate the exhaust purification filter PF. Do it regularly accordingly.

  During the filter regeneration process for regenerating the exhaust gas purification filter PF of the exhaust gas purification device DPF, the adhered carbon particles are burned and the exhaust gas EG of 600 ° C. or more (eg, 700 ° C. to 900 ° C.) is discharged. . That is, during the filter regeneration process, the exhaust gas EG having a high temperature equal to or higher than the first temperature (600 ° C.) continues to be discharged from the exhaust gas purification device DPF. Therefore, during the filter regeneration process, the temperature of the exhaust gas EG (measurement gas) reaching the particulate sensor 10 becomes equal to or higher than the first temperature (600 ° C.).

  However, when the temperature of the exhaust gas EG reaching the particulate sensor 10 reaches a high temperature equal to or higher than the first temperature (600 ° C.), the inner protector 60 (first discharge electrode) and the discharge electrode body 130 of the ceramic element 120 (second discharge electrode) And the insulation resistance between the In this state, when the second potential PV2 is applied to the discharge electrode body 130 (when the first voltage is applied between the inner protector 60 and the discharge electrode body 130), a member of the same potential as the inner protector 60 (or the inner protector 60) There is a possibility that spark discharge may be generated instead of corona discharge between the member having the first potential PV1) and the discharge electrode body 130. When such a spark discharge occurs, there is a possibility that a defect may occur in the particulate matter detection system 1.

  Also, under such a high temperature environment, insulation of the surface of the insulator (ceramic base 121) to which a part of the discharge electrode body 130 (the tip side portion 131s of the needle-like electrode portion 131 and the discharge potential pad 135) is exposed. Since the resistance is also greatly reduced, the spark discharge described above is from the discharge electrode body 130 (for example, the tip side portion 131s of the needle-like electrode portion 131) via the surface of the ceramic substrate 121 (for example, the ceramic layer 122 or 123). In some cases (surface discharge of the surface of the ceramic base 121 may occur). When such a spark discharge occurs, a trace of the discharge remains on the surface of the ceramic substrate 121 (the path where the surface discharge occurs), and thereafter, the temperature of the exhaust gas EG reaching the particulate sensor 10 is a high temperature higher than the first temperature (600 ° C.) Even if the exhaust gas EG does not reach the normal temperature (for example, when the exhaust gas EG reaches a normal temperature), the creeping discharge through this discharge mark tends to be generated, and there is a possibility that the above-mentioned corona discharge can not be generated properly. Therefore, there is a possibility that the particulates S in the exhaust gas EG can not be properly detected.

  On the other hand, in the present embodiment, when the regeneration-in-progressing signal SR indicating that the filter regeneration processing of the exhaust gas purification device DPF is in progress is output from the ECU, the determination unit 220 ) Is received from the ECU, and it is determined that the signal SR during regeneration is received. Then, if the determination unit 220 determines that the in-reproduction signal SR is received, the voltage reduction instruction unit 230 instructs the discharge voltage output unit 210 to set the output stop state (do not output the voltage). By this instruction, discharge voltage output unit 210 stops applying second potential PV2 to discharge electrode body 130 (second discharge electrode) (stops output of second potential PV2), The electric potential is set to the same first electric potential PV1 as the inner protector 60.

  As a result, even if the temperature of the exhaust gas EG reaching the particulate matter sensor 10 reaches a high temperature equal to or higher than the first temperature (600 ° C.) by the filter regeneration process of the exhaust gas purification device DPF, the same effect as the inner protector 60 (or the inner protector 60) It is possible to prevent the occurrence of spark discharge (including spark discharge via the surface of the ceramic base 121) between the member of the potential and the member of the first potential PV1) and the discharge electrode body 130.

Next, the flow of particulate detection in the present embodiment will be described. FIG. 8 is a flowchart showing the flow of particle detection according to the embodiment.
When a key switch (not shown) of the engine is turned on, in step S1, the determination unit 220 of the control device 200 determines whether there is a particle detection start instruction from the ECU. Specifically, the determination unit 220 determines the presence or absence of the particulate signal detection start instruction signal ST (see FIG. 4). If it is determined that the instruction signal ST is not present (NO), step S1 is repeated to wait for the input of the particle detection start instruction signal ST from the ECU. If the instruction signal ST is detected (YES), the process proceeds to step S2.

  In step S2, the determination unit 220 determines whether the filter regeneration process of the exhaust gas purification device DPF is in progress. Specifically, it is determined whether a regeneration-in-progress signal SR indicating that the filter regeneration process of the exhaust gas purification device DPF is in progress is received. In the present embodiment, as described above, it can be determined that “the filter regeneration process of the exhaust gas purification device DPF is in progress” as “the temperature of the exhaust gas EG (measured gas) that reaches the particulate sensor 10 Is equivalent to the determination of "whether or not the prediction condition that can be predicted when the temperature becomes the first temperature (600.degree. C.) holds". Further, since the in-reproduction signal SR is continuously transmitted from the ECU during the filter regeneration process, the determination unit 220 continuously receives the in-reproduction signal SR during the filter regeneration process. .

  If it is determined that the signal SR during reproduction is not received (NO), the process proceeds to step S3, and the control device 200 drives the particulate sensor 10 to perform particulate detection processing. Specifically, as described above, the second potential PV2 is applied to the discharge electrode body 130 of the ceramic element 120 by the discharge voltage output unit 210 to generate the ion CP by corona discharge, and the charge amount of the discharge ion CPH The particle detection unit 260 performs predetermined particle detection processing such as detecting the signal current Is corresponding to.

  Next, in step S4, the determination unit 220 determines whether a key switch (not shown) of the engine ENG is turned off. Determination unit 220 acquires on / off information of the key switch of engine ENG from the ECU. Then, if it is determined that the key switch of engine ENG is not OFF (NO), the processes of steps S2 and S3 described above are repeated. Thereafter, when it is determined that the key switch of the engine ENG is OFF (YES), a series of processing is ended.

  On the other hand, if it is determined in step S2 that the signal SR during regeneration is received (YES), the process proceeds to step S5, and the voltage reduction instructing unit 230 causes the discharge voltage output unit 210 to stop output. Instructs (do not output voltage). By this instruction, discharge voltage output unit 210 stops applying second potential PV2 to discharge electrode body 130 (second discharge electrode) (stops output of second potential PV2), The electric potential is set to the same first electric potential PV1 as the inner protector 60. This prevents the occurrence of the spark discharge described above.

  Next, the process returns to step S2, and the determination unit 220 determines again whether the filter regeneration process of the exhaust gas purification device DPF is in progress. If it is determined that the in-reproduction signal SR is received (YES), the process proceeds to step S5, and the voltage reduction instructing unit 230 instructs the discharge voltage output unit 210 to set the output stop state. As a result, during the filter regeneration process of the exhaust purification device DPF, the output voltage stop state is continued in the discharge voltage output unit 210, and the generation of the spark discharge described above is continuously prevented.

  Thereafter, when it is determined in step S2 that the signal SR during regeneration is not received (NO), the process proceeds to step S3, and the above-described particle detection processing is performed. Thereafter, when it is determined in step S4 that the key switch of the engine ENG is off (YES), a series of processing is ended.

(Modification 1)
A first variant of the invention will now be described with reference to the drawings.
The particulate matter detection system 301 of Modification 1 is different from the particulate matter detection system 1 of the embodiment in the control device, and the other points are the same.
Specifically, in the embodiment, the determination unit 220 of the control device 200 determines whether the temperature of the exhaust gas EG (gas to be measured) reaching the particulate sensor 10 is 1st depending on whether or not the regeneration signal SR is received from the ECU. It was judged whether the prediction conditions which can be predicted to become higher than the temperature (600 ° C.) were satisfied. On the other hand, in the first modification, the determination unit 420 of the control device 400 determines that the temperature of the exhaust gas EG (gas to be measured) that has reached the particulate sensor 10 is higher than the first temperature (600 ° C.) as follows. It is determined whether the

  Specifically, as shown in FIG. 9, the control device 400 of the first modified embodiment has a voltage output unit 250 and a measurement control unit 480. The measurement control unit 480 includes a temperature detection unit 490 in addition to the determination unit 420, the voltage reduction instruction unit 230, the particle detection unit 260, and the heater energization unit 270. The temperature detection unit 490 detects the temperature of the exhaust gas EG (measurement gas) that has reached the particulate sensor 10 by using (also used as) the heating resistor 151 of the ceramic element 120 as a temperature detection element. The element tip portion 120s of the ceramic element 120 where the heating resistor 151 is disposed is in contact with the intake gas EGI taken into the inner protector 60 of the exhaust gas EG flowing in the exhaust pipe EP (see FIG. 7), the temperature of the exhaust gas EG that has reached the particulate sensor 10 can be appropriately detected by the heating resistor 151.

  The heating resistor 151 is made of tungsten and has a characteristic that its own resistance value changes in accordance with its own temperature change. Therefore, by measuring the resistance value of the heating resistor 151, the temperature of the heating resistor 151 can be detected from the resistance value. In the first modification, the temperature of the heating resistor 151 is regarded as the temperature of the exhaust gas EG (the measurement gas), and the temperature of the exhaust gas EG is detected.

  Specifically, the temperature detection unit 490 measures the value of the current flowing through the heating resistor 151 when a constant voltage is applied to the heating resistor 151, and generates the heating resistor from the applied voltage value and the measured current value. The resistance value of the body 151 is detected. Furthermore, in the temperature detection unit 490, correlation data between the resistance value of the heating resistor 151 and the temperature which are grasped in advance are stored. Therefore, the temperature detection unit 490 detects the temperature of the heating resistor 151 based on the detected resistance value and the correlation data, and regards the detected temperature Tg as the temperature of the exhaust gas EG.

  Then, the determination unit 420 determines whether the temperature Tg detected by the temperature detection unit 490 is equal to or higher than the first temperature (600 ° C.). In this manner, in the first modified embodiment, the determination unit 420 determines whether the temperature of the exhaust gas EG (gas to be measured) that has reached the particulate sensor 10 is equal to or higher than the first temperature (600 ° C.). Further, voltage reduction instruction unit 230 outputs the voltage output from discharge voltage output unit 210 to discharge voltage output unit 210 when determination unit 220 determines that detected temperature Tg is equal to or higher than the first temperature (600 ° C.). Are instructed to be reduced to a second voltage lower than the first voltage (= second potential PV2−first potential PV1). Specifically, it instructs the discharge voltage output unit 210 to set the output stop state (do not output the voltage).

Next, the flow of particle detection in the first modification will be described. FIG. 10 is a flow chart showing the flow of particle detection according to the first modification.
When a key switch (not shown) of the engine is turned on, in step T1, the determination unit 420 of the control device 400 determines whether there is a particulate detection start instruction from the ECU. Specifically, determination unit 420 determines the presence or absence of particulate detection start instruction signal ST (see FIG. 9). When it is determined that the instruction signal ST is not present (NO), step T1 is repeated to wait for the input of the particle detection start instruction signal ST from the ECU. If the instruction signal ST is detected (YES), the process proceeds to step T2.

In step T2, as described above, the temperature detection unit 490 detects the temperature of the exhaust gas EG (gas to be measured) that has reached the particulate sensor 10.
Next, proceeding to step T3, the determination unit 420 determines whether the temperature Tg detected by the temperature detection unit 490 is equal to or higher than the first temperature (600 ° C.).

  If it is determined in step T3 that the detected temperature Tg is not higher than the first temperature (600 ° C.) (NO), the process proceeds to step T4, and the control device 400 drives the particle sensor 10 as in the embodiment. , Perform particle detection processing. Specifically, the second potential PV2 is applied to the discharge electrode body 130 of the ceramic element 120 by the discharge voltage output unit 210 to generate the ion CP by corona discharge, and a signal current corresponding to the charge amount of the discharge ion CPH. A predetermined particle detection process is performed, such as detection of Is by the particle detection unit 260.

  Subsequently, the process proceeds to step T5, and the determination unit 420 determines whether the key switch (not shown) of the engine ENG is turned off, as in the determination unit 220 of the embodiment. Then, if it is determined that the key switch of engine ENG is not OFF (NO), the processes of steps T2 to T4 described above are repeated. Thereafter, when it is determined that the key switch of the engine ENG is OFF (YES), a series of processing is ended.

  On the other hand, if it is determined in step T3 that the detected temperature Tg is equal to or higher than the first temperature (600 ° C.) (YES), the process proceeds to step T6 and the voltage reduction instruction unit 230 sends a signal to the discharge voltage output unit 210. Instructs to stop the output (do not output the voltage). By this instruction, discharge voltage output unit 210 stops applying second potential PV2 to discharge electrode body 130 (second discharge electrode) (stops output of second potential PV2), The electric potential is set to the same first electric potential PV1 as the inner protector 60. This prevents the occurrence of the spark discharge described above.

  Next, the process returns to step T2, and the temperature detection unit 490 detects the temperature of the exhaust gas EG (gas to be measured) that has reached the particle sensor 10 again, and then in step T3, the determination unit 420 detects the detected temperature Tg It is determined whether it is the first temperature (600 ° C.) or more. If it is determined that the detected temperature Tg is equal to or higher than the first temperature (600 ° C.) (YES), the process proceeds to step T6, and the voltage reduction instructing unit 230 causes the discharge voltage output unit 210 to stop output. To indicate. As a result, the output stop state is continued in the discharge voltage output unit 210, and the generation of the spark discharge described above is continuously prevented.

  Thereafter, when it is determined in step T3 that the detected temperature Tg is not higher than the first temperature (600 ° C.) (NO), the process proceeds to step T4, and the above-described particulate detection process is performed. Thereafter, when it is determined in step T5 that the key switch of the engine ENG is off (YES), the series of processes is ended.

(Modification 2)
A second variant of the invention will now be described with reference to the drawings.
The particulate matter detection system 501 of Modification 2 is different from the particulate matter detection system 1 of the embodiment in the structure of the particulate matter sensor, and the other points are the same.
The particulate sensor 10 according to the embodiment has a structure in which the discharge electrode body 130 (specifically, the tip side portion 131s of the needle electrode portion 131) contacts the exhaust gas EG, as shown in FIG. On the other hand, as shown in FIG. 11, the particulate matter sensor 510 according to the second modification has a structure in which the discharge electrode body 520 (needle-like distal end 522) does not contact the exhaust gas EG.

  Note that FIG. 11 illustrates only the portion (the tip of the particle sensor 510) of the particle detection system 501 disposed in the exhaust pipe EP. The tip of the particle sensor 510 has a casing 560 and a needle tip 522 of the discharge electrode 520 disposed therein. The casing 560 has a nozzle portion 531, an inlet 533, an outlet 543, and the like, which will be described later. The discharge electrode body 520 (second discharge electrode) is held by the cylindrical ceramic 575 (insulator), and a part of the discharge electrode body 520 (needle-like tip portion 522) is exposed (projected) from the cylindrical ceramic 575 doing.

  In the particulate matter detection system 501 of the second modification, between the nozzle portion 531 (first discharge electrode) set to the first potential PV1 and the needle-like tip 522 (second discharge electrode) set to the second potential PV2 The corona discharge is generated to generate ions CP around the needle tip 522. A part of the generated ions CP is jetted toward the mixing area MX through the nozzle hole 531N together with the compressed air AR supplied to the discharge space DS. Furthermore, since the pressure of the mixing area MX is lowered by the flow of the air AR injected at high speed, the exhaust gas EG outside the inlet 533 is taken into the mixing area MX from the inlet 533 through the lead-in passage HK. The intake gas EGI taken in is mixed with the air AR containing the ions CP in the mixing area MX, and is discharged from the discharge port 543 via the discharge passage EX together with the air AR.

  At this time, if the exhaust gas EG contains particulates S such as soot, the particulates S are also taken into the mixing region MX. For this reason, the introduced particles S adhere to the ions CP and become positively charged charged particles SC. In this state, they are discharged together with the air AR from the discharge port 543 through the mixing area MX and the discharge path EX. Be done. In the particle detection system 501 as well, as in the embodiment, the particle detection unit 260 uses a signal (signal current Is) corresponding to the charge amount of the discharge ion CPH attached to the charged particles SC discharged from the discharge port 543. By detecting, the amount (concentration) of the particulates S contained in the exhaust gas EG is detected.

  In the particulate matter detection system 501, as described above, since the compressed air AR is injected from the discharge space DS toward the mixing area MX through the nozzle holes 531N, the exhaust gas EG taken into the mixing area MX (intake gas EGI) is not taken into the discharge space DS. Therefore, the exhaust gas EG (fine particles S) does not contact the needle-like tip end 522 of the discharge electrode body 520 located in the discharge space DS.

  As described above, even in the particulate detection system 501 according to the second modification, in which the discharge electrode body 520 (the needle tip 522) is not in contact with the exhaust gas EG (the particulate S), the filter regeneration process of the exhaust purification device DPF is performed. When the temperature of the exhaust gas EG reaching the particulate matter sensor 510 is a high temperature equal to or higher than the first temperature (600.degree. C.), between the discharge electrode body 520 (second discharge electrode) and the nozzle portion 531 (first discharge electrode) And the insulation resistance of the surface of the cylindrical ceramic 575 are greatly reduced. Therefore, a spark discharge (surface of the cylindrical ceramic 575 is formed between the discharge electrode body 520 (needle-like tip 522) and the nozzle portion 531 (or a member having the same potential as the first potential PV1). There is a possibility that the spark discharge (including the spark discharge) may occur.

  On the other hand, also in the second modification, as in the embodiment, the determination unit 220 determines whether the regeneration signal SR indicating that the filter regeneration processing of the exhaust gas purification device DPF is in progress has been received or not. When it is determined in section 220 that the signal SR during regeneration is received, voltage reduction instructing section 230 instructs discharge voltage output section 210 to put the output in the stop state (do not output the voltage). This can prevent the above-described spark discharge from occurring.

  Although the present invention has been described based on the embodiment and the first and second modifications, the present invention is not limited to the above embodiment and the like, and can be appropriately modified without departing from the scope of the invention. It goes without saying that it is applicable.

For example, in the embodiment, it is determined in step S2 whether or not the regeneration in-progress signal SR indicating that the filter regeneration processing of the exhaust gas purification device DPF is in progress has been received. Whether or not a prediction condition that can be predicted that the temperature of the gas to be measured becomes equal to or higher than the first temperature is established is determined. That is, in the embodiment, whether or not the signal SR during reproduction is received is set as the above-mentioned prediction condition.

  However, for example, as shown by a broken line in FIG. 1, when the exhaust pipe EP on the upstream side of the particulate sensor 10 is provided with the temperature sensor 3 for detecting the temperature of the exhaust gas EG, this temperature sensor 3 detects When the detected temperature of the exhaust gas EG becomes equal to or higher than the first temperature (for example, 600 ° C.), it can be predicted that the temperature of the exhaust gas EG reaching the particulate sensor 10 becomes equal to or higher than the first temperature. For this reason, in this case, it can be set as a prediction condition that "the detection temperature which temperature sensor 3 detected is more than the 1st temperature." Therefore, for example, in step S2, the determination unit 220 may receive the detected temperature detected by the temperature sensor 3 and determine whether the detected temperature is equal to or higher than the first temperature. When the temperature detected by the temperature sensor 3 is equal to or higher than the first temperature, the voltage reduction instructing unit 230 causes the discharge voltage output unit 210 to stop output (does not output the voltage) in step S5. You may instruct it.

  Further, also when the engine ENG is continuously operated at a high load and high speed for a predetermined time (for example, 5 seconds) when the vehicle AM climbs a long slope, and the high temperature exhaust gas EG is continuously discharged, The temperature of the exhaust gas EG reaching the particulate sensor 10 becomes equal to or higher than the first temperature (e.g., 600 ° C.). Therefore, when the operating condition of the engine ENG is high load and high rotation, and this continues for a predetermined time (for example, 5 seconds), it can be predicted that the temperature of the exhaust gas reaching the particulate sensor 10 becomes equal to or higher than the first temperature. Therefore, for example, in step S2, based on the operating conditions of the internal combustion engine including the rotational speed of the engine ENG, the accelerator opening degree, etc., the determination unit 220 receives from the ECU etc. high load high for a predetermined time (for example 5 seconds) Whether or not the prediction condition is satisfied may be determined by determining whether or not the rotation operation condition is indicated. When it is determined that the prediction condition is satisfied, the voltage reduction instructing unit 230 instructs the discharge voltage output unit 210 to set the output stop state (do not output the voltage) in step S5. Also good.

1, 301, 501 particle detection system 3 temperature sensor 10, 510 particle sensor 20 inner metal fitting 25 gas intake pipe 30 main metal fitting 40 inner cylinder 60 inner protector (first discharge electrode)
60e Gas outlet 65 Outer protector 65c Gas intake 70 Outer bracket 80 Mounting bracket 90 Outer cylinder 120 Ceramic element 121 Ceramic base (insulator)
130 Discharge electrode body (second discharge electrode)
DESCRIPTION OF SYMBOLS 131 Needle-like electrode part 140 Auxiliary electrode body 150 Heater for elements 151 Heat-generating resistor 200, 400 Control device 210 Discharge voltage output part 220, 420 Determination part 230 Voltage reduction indication part 490 Temperature detection part 520 Discharge electrode body (2nd discharge electrode )
531 Nozzle (First Discharge Electrode)
575 Tubular ceramic (insulator)
AM Vehicle CP Ion DPF Exhaust purification device ECU Engine control unit (internal combustion engine control device)
EG exhaust gas (gas to be measured)
EGI intake gas ENG engine (internal combustion engine)
EP Exhaust pipe (vent)
PF exhaust purification filter S fine particles

Claims (2)

A second discharge electrode that generates a corona discharge between the first discharge electrode, the insulator, and the first discharge electrode, wherein the second discharge electrode is held by the insulator and a part of the second discharge electrode is the insulator A particulate sensor having a second discharge electrode exposed from the body, and
A controller for controlling the particle sensor;
A first voltage is applied between the first discharge electrode and the second discharge electrode by the control of the control device in a state in which the particle sensor is attached to a vent pipe through which a gas to be measured containing the particle flows. The particle detection system generates the corona discharge to generate ions around the second discharge electrode, and detects the particles in the gas to be measured using the ions.
The control unit
A discharge voltage output unit that outputs a first voltage applied between the first discharge electrode and the second discharge electrode to generate a corona discharge between the first discharge electrode and the second discharge electrode When,
Whether or not a prediction condition that can predict that the temperature of the gas to be measured that reaches the particle sensor reaches or exceeds the first temperature is satisfied, and the temperature of the gas to be measured that has reached the particle sensor is above the first temperature A determination unit that determines at least one of whether or not there is a
In the determination section, the discharge voltage is determined when at least one of the determination that the prediction condition is satisfied and the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature And a voltage reduction instructing unit instructing the output unit to reduce the voltage output from the discharge voltage output unit to a second voltage lower than the first voltage .
The second voltage is the same as the second discharge electrode, the first discharge electrode, and the first discharge electrode in a state where the temperature of the gas to be measured which has reached the particle sensor reaches or exceeds the first temperature. Between the members of the potential and the size where spark discharge does not occur,
The voltage reduction instruction unit
The discharge voltage when the determination unit determines that the prediction condition is satisfied and at least one of the temperature of the gas to be measured that has reached the particle sensor is equal to or higher than the first temperature. The particle detection system , which instructs the output unit to stop the output of the discharge voltage output unit . The particle detection system according to claim 1, wherein
The vent pipe is an exhaust pipe through which exhaust gas of an internal combustion engine flows,
The measured gas is the exhaust gas,
The exhaust pipe is provided with an exhaust gas purification device having an exhaust gas purification filter inside on the upstream side of the particulate matter sensor,
The determination unit is
Whether the filter regeneration process is performed to burn the carbon particles collected by the exhaust gas purification filter in the exhaust gas purification device and regenerate the exhaust gas purification filter as a judgment as to whether the prediction condition is satisfied or not To determine
The voltage reduction instruction unit
The particulate matter detection system according to claim 1 , wherein , when it is determined that the filter regeneration process is in progress in the determination unit, the discharge voltage output unit is instructed to stop the output of the discharge voltage output unit .

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