JP2019095199A - Particle detection device - Google Patents

Abstract

To enable appropriately detecting the amount of fine particles at the start of an engine while attaching the fine particle sensor to the exhaust pipe of a direct injection gasoline engine.SOLUTION: A fine particle detection device controls the fine particle sensor attached to the exhaust pipe of a direct injection gasoline engine. The fine particle sensor includes a detection unit, an insulating member, and a heating unit. The detection unit is configured to electrify fine particles contained in the exhaust gas flowing into its interior to generate charged fine particles. The detection performance decreases when the insulating material is formed in contact with the exhaust gas and fine particles adhere to the gas contact surface. The heating unit heats the gas contact surface. The fine particle detection device performs heating by the heating unit so that the evaporation temperature water evaporates on the gas contact surface when the engine is started. The fine particle detection device calculates the amount of fine particles, and outputs the fine particle amount information.SELECTED DRAWING: Figure 10

Description

  The present disclosure relates to a particle detector that detects the amount of particles contained in exhaust gas discharged from a direct injection gasoline engine.

  In the past, in order to collect particulates contained in exhaust gas of an internal combustion engine, a filter member has been provided in the middle of the exhaust pipe. However, since this filter member is repeatedly exposed to high heat due to the execution of a regeneration treatment that burns and removes the high temperature exhaust gas and the collected fine particles, the filter member may cause cracks, defects and the like. In this case, part of the exhaust gas is discharged to the outside as it is without the particulate matter being collected by the filter member. That is, a failure (collection efficiency reduction failure) may occur in which the collection efficiency of particulates in the filter member is reduced.

  Therefore, if the particulate matter sensor is attached to the downstream side of the filter member in the exhaust pipe of the internal combustion engine, and the amount of particulate matter detected by the particulate matter sensor exceeds the threshold value, it indicates that the collection efficiency declines. It is proposed to make a fault diagnosis of the filter member in such a way as to make a determination. And as such a particulate sensor, a pair of electrodes are provided on the substrate separated from each other, particulates are attached and deposited between the electrodes, and the resistance between the electrodes is lowered as the amount of deposited particulates increases. There is known a so-called resistance-change-type particulate sensor that detects the amount of particulates in exhaust gas (see Patent Document 1).

JP 2012-122399 A

  By the way, as a type of internal combustion engine, there is a direct injection gasoline engine which is a gasoline engine which directly injects fuel which is fuel into a combustion chamber at high pressure. And in this direct injection gasoline engine, it is known that the amount of particles discharged at the time of cold start is larger than the amount of particles discharged after the engine temperature rises. Therefore, when a direct injection gasoline engine is started, a method is conceivable to detect the amount of fine particles using a fine particle sensor and diagnose failure of the filter member (gasoline, particulate filter). Since the condensed water generated by the like flows through the exhaust pipe, the resistance change type particle sensor can not detect the amount of particles discharged at the time of cold start. In the resistance change type particle sensor, if condensed water adheres across the electrodes, the resistance between the electrodes decreases regardless of the amount of the particles, causing a problem of erroneous detection, and the condensed water adhered between the electrodes If the substrate is heated by the heater to evaporate the adhesion of the particles between the electrodes, the amount of particles can not be detected properly. Furthermore, the resistance change type particulate sensor is a principle that deposits particulates over a predetermined period to obtain a signal related to the amount of the particulates, so it is not suitable for detection in a short period such as cold start.

  An object of the present disclosure is to attach a particulate matter sensor to an exhaust pipe of a direct injection gasoline engine, and to appropriately detect the amount of particulates at the time of starting the engine.

One aspect of the present disclosure is a particulate detection device that is attached to an exhaust pipe of a direct injection gasoline engine and controls a particulate sensor that detects the amount of particulates contained in exhaust gas in the exhaust pipe.
And a particulate sensor is provided with a detection part, an insulating member, and a heating part. The detection unit is configured to charge the particulates contained in the exhaust gas flowing into the inside thereof to generate charged particulates. The insulating member is formed to have a gas contact surface in contact with the exhaust gas, and when particulates adhere to the gas contact surface, the detection performance of the detection unit is reduced. The heating portion is configured to heat at least a portion of the gas contacting surface.

  The particulate matter detection device further includes a heating execution unit and an information output unit. The heating execution unit is configured to execute heating by the heating unit so as to reach an evaporation temperature at which water is evaporated on the gas contact surface when the direct injection gasoline engine is started. The information output unit is configured to calculate the amount of particles using a signal current flowing based on the charged particles, and to output particle amount information indicating the amount of particles.

  In the particle detection device of the present disclosure configured as described above, first, unlike the resistance change type particle sensor, the detection unit charges the particles in the exhaust gas flowing into the inside thereof to generate charged particles. Is configured as. By using this detection unit, it is not necessary to deposit fine particles between electrodes for a predetermined period as in a resistance change type fine particle sensor, and the amount of fine particles is calculated in real time using signal current flowing based on charged fine particles. It becomes possible to detect the amount of particulates immediately after the start of the direct injection gasoline engine. However, even if the particulate matter detection device has a detection unit configured to charge the particulates in the exhaust gas, if the particulate matter adheres to the gas contact surface, the detection performance of the detection unit decreases. When the insulating member is provided, the amount of particulates may not be properly detected unless adhesion of condensed water to the gas contact surface at the time of cold start is suppressed.

  Therefore, in the particulate matter detection device of the present disclosure, when the direct injection gasoline engine is started, the gas contact surface is heated to have an evaporation temperature at which water is evaporated on the gas contact surface. For this reason, the particulate matter detection device of the present disclosure evaporates the condensed water generated at the time of cold start of the direct injection gasoline engine on the gas contact surface, and exerts the thermophoretic force based on the heating of the heating unit on the condensed water. Thus, the condensed water can be moved away from the gas contact surface to prevent the condensed water from adhering to the gas contact surface. That is, in the fine particle detection device of the present disclosure, condensed water adheres to the gas contact surface and the insulation performance of the insulating member decreases, as the fine particles adhere to the gas contact surface and the insulation performance of the insulating member decreases. The reduction of the detection performance of the detection unit can be suppressed. Thereby, the particulate matter detection device of this indication can detect the amount of particulates at the time of cold start of a direct injection gasoline engine.

  Further, in one aspect of the present disclosure, the evaporation temperature may be 200 ° C. or higher. Thereby, the particle detecting device of the present disclosure can further suppress adhesion of condensed water to the gas contact surface by the thermophoretic force based on heating of the heating unit, and can improve the detection accuracy of the amount of particles. it can.

  Further, in one aspect of the present disclosure, the detection unit includes a discharge electrode body including a discharge unit configured to generate ions by corona discharge, and causes the generated ions to adhere to the particles contained in the exhaust gas. It may be configured to be charged. Furthermore, the insulating member may cover the discharge electrode body with the discharge portion exposed, and the gas contact surface may be the periphery of the discharge portion in the insulating member.

  The particulate matter detection device of the present disclosure thus configured heats the periphery of the discharge portion so as to reach an evaporation temperature at which water evaporates around the discharge portion when the direct injection gasoline engine is started. For this reason, the particulate matter detection device of the present disclosure can suppress the occurrence of a situation where the condensed water adheres to the discharge portion and the corona discharge can not be generated in the discharge portion.

  In one aspect of the present disclosure, the particulate sensor includes an inner fitting and an outer fitting, and the insulating member is disposed between the inner and outer fittings to electrically connect the inner and outer fittings. It may be insulated. The inner fitting has a gas intake pipe for introducing exhaust gas therein, is at a potential different from that of the exhaust pipe, and is included in the detection unit. The outer fitting surrounds the inner fitting, is attached to the exhaust pipe, and is electrically connected to the exhaust pipe.

  In the particulate matter detection device of the present disclosure thus configured, when the direct injection gasoline engine is started, condensed water adheres to the gas contact surface of the insulating member disposed between the inner and outer fittings. It is possible to suppress the decrease in the insulation performance of the insulating member between the inner and outer metal fittings. As a result, in the particulate matter detection device of the present disclosure, occurrence of a situation where the detection performance of the detection unit is lowered due to the leak current flowing between the inner and outer metal fittings due to the condensed water adhering to the gas contact surface. It can be suppressed.

It is a figure which shows schematic structure of the system which has a sensor control apparatus as a component. It is a sectional view of a particulate sensor. It is a disassembled perspective view of a particulate sensor. It is a perspective view of the insulation spacer from the front end side. It is a perspective view of the insulation spacer from the back end side. It is a perspective view of a ceramic element. It is a disassembled perspective view of a ceramic element. It is a figure which shows the circuit structure of a sensor control apparatus. It is a schematic diagram for demonstrating the detection operation of a particulate sensor. It is a flow chart which shows sensor control processing. It is a graph which shows the detection result by a current detection circuit.

Embodiments of the present disclosure will be described below with reference to the drawings.
The sensor control device 1 of the present embodiment is mounted on a vehicle, and controls the particulate sensor 2 as shown in FIG.

  The sensor control device 1 is configured to be able to transmit and receive data via the communication line 5 with the electronic control device 4 that controls the direct injection gasoline engine 3. Hereinafter, the electronic control device 4 is referred to as an engine ECU 4. ECU is an abbreviation of Electronic Control Unit.

  The particulate sensor 2 is attached to the exhaust pipe 6 of the direct injection gasoline engine 3 of the vehicle, and detects the amount of particulate (for example, soot) contained in the exhaust gas in the exhaust pipe 6. In addition, since the configuration of the direct injection gasoline engine 3 is known, the description in the present embodiment is omitted.

  The particulate sensor 2 includes a casing 11, a ceramic element 12, and a cable 13, as shown in FIG. In FIG. 2, the lower end side of the particulate sensor 2 is referred to as a front end side FE, the upper end side of the particulate sensor 2 is referred to as a rear end BE, and the longitudinal direction of the particulate sensor 2 is referred to as an axial direction DA.

The casing 11 holds the ceramic element 12 so that the tip end side FE of the ceramic element 12 protrudes into the inside of the exhaust pipe 6.
The casing 11 includes an inner fitting 21, an outer fitting 22, insulating spacers 23 and 24, an insulating holder 25, and separators 26 and 27.

The inner fitting 21 includes a metal shell 31, a gas intake pipe 32, an inner cylinder 33, and an inner cylinder connection fitting 34.
The metal shell 31 is a stainless steel member formed in a tubular shape extending in the axial direction DA. The metal shell 31 includes a main body portion 41 and a flange portion 42. The main body portion 41 is formed in a cylindrical shape extending in the axial direction DA, and includes a through hole 41a penetrating along the axial direction DA, and a shelf 41b projecting inward in the radial direction of the through hole 41a. The shelf portion 41b is formed as an inward taper surface having an inclination from the radially outer side to the center of the through hole 41a toward the tip end side FE. The flange portion 42 is formed in a plate shape extending outward from the outer periphery of the main body portion 41 in the radial direction.

  Inside the through hole 41 a of the metal shell 31 are a ceramic holder 43 which is a cylindrical member surrounding the periphery of the ceramic element 12 in the radial direction from the front end side FE to the rear end side BE, and a powder filled layer. Talc rings 44, 45 and a ceramic sleeve 46 are stacked.

  A clamping ring 47 is disposed between the ceramic sleeve 46 and the end of the rear end BE of the metal shell 10. A metal holder 48 is disposed between the ceramic holder 43 and the shelf 41 b of the metal shell 10. The metal holder 48 holds the talc ring 44 and the ceramic holder 43. The end of the rear end side BE of the metal shell 31 is a portion crimped so as to press the ceramic sleeve 46 toward the front end side FE via the caulking ring 47.

  The gas intake pipe 32 is provided at the end of the front end side FE of the metal shell 31, and includes an outer protector 51 and an inner protector 52. The outer protector 51 and the inner protector 52 are stainless steel members formed in a tubular shape extending in the axial direction DA. The inner protector 52 is welded to the metal shell 31 in a state of covering the end of the tip end side FE of the ceramic element 12, and the outer protector 51 is welded to the metal shell 31 in a state of covering the inner protector 52.

  The inner cylinder 33 is a stainless steel member formed in a cylindrical shape extending in the axial direction DA. The inner cylinder 33 includes a main body portion 54 and a flange portion 55. The main body portion 54 is formed in a cylindrical shape extending in the axial direction DA, and includes a through hole 54a penetrating along the axial direction DA. The flange portion 55 is formed in a plate shape extending outward in the radial direction from the outer periphery of the end portion of the distal end side FE in the main body portion 54. The inner cylinder 33 is in a state where the end of the rear end BE of the metal shell 31 is fitted into the opening of the end of the front end FE, that is, in the state where the flange 55 is overlapped with the flange 42 of the metal shell 31. , Is welded to the metal shell 31.

Inside the through hole 54a of the inner cylinder 33, an insulation holder 25, a separator 26, and a separator 27 are stacked in order from the front end side FE to the rear end side BE.
The insulating holder 25 is a tubular insulating member surrounding the periphery of the ceramic element 12 in the radial direction.

  The separator 26 is a cylindrical insulating member extending in the axial direction DA. The separator 26 is formed with a through hole 26 a penetrating along the axial direction DA. The ceramic element 12 is inserted into the through hole 26 a such that the ceramic element 12 protrudes from the end of the rear end side BE of the separator 26.

  The separator 27 is a cylindrical insulating member extending in the axial direction DA. The end of the rear end side BE of the ceramic element 12 is inserted into the separator 27. The separator 27 is formed with a through hole 27 a and a through hole 27 b penetrating along the axial direction DA. The outer surface of the separator 27 is formed with a flange portion 27 c that protrudes outward in the radial direction.

  The end of the rear end side BE of the inner cylinder 33 is crimped so as to press the flange portion 27c toward the front end side FE. Thus, the insulating holder 25, the separators 26 and the separators 27 are held fixed to the inner cylinder 33.

  The inner cylinder connection fitting 34 is a cylindrically formed stainless steel member in which the end of the rear end side BE is closed. The inner cylinder connection fitting 34 is welded to the inner cylinder 33 with the end of the rear end BE of the inner cylinder 33 fitted in the opening at the end of the front end FE. At the end of the rear end side BE of the inner cylinder connection fitting 34, a plurality of insertion openings 34a for inserting the cable 13 are formed.

  The outer fitting 22 includes a mounting fitting 61 and an outer cylinder 62. The mounting fitting 61 is a stainless steel member formed in a cylindrical shape extending in the axial direction DA. The mounting bracket 61 includes a main body portion 71 and a hexagonal portion 72. The main body 71 is formed in a cylindrical shape extending in the axial direction DA, and includes a through hole 71a penetrating along the axial direction DA, and a shelf 71b projecting inward in the radial direction of the through hole 71a. The shelf portion 71b is formed as an inward taper surface having an inclination from the radially outer side to the center of the through hole 71a toward the tip end side FE. An external thread for fixing to the exhaust pipe 6 is formed on the outer periphery of the distal end side FE in the main body portion 71. The hexagonal portion 72 extends outward in the radial direction from the outer periphery of the rear end side BE in the main body portion 71, and the outer periphery is formed in a hexagonal plate shape.

  The exhaust pipe 6 is formed with an insertion port 6 a for inserting the particulate sensor 2. The mounting boss 6 b is attached to the outer peripheral surface of the exhaust pipe 6 so as to protrude from the insertion port 6 a. Therefore, the particle sensor 2 is inserted into the screw hole of the mounting boss 6b, and the male screw of the mounting bracket 61 is screwed into the female screw formed on the inner peripheral wall of the screw hole of the mounting boss 6b. The particulate sensor 2 is attached to the exhaust pipe 6 such that the intake pipe 32 protrudes from the inner circumferential surface of the exhaust pipe 6.

  The outer cylinder 62 is a stainless steel member formed in a cylindrical shape extending in the axial direction DA. The outer cylinder 62 includes a large diameter portion 74 and a small diameter portion 75. The large diameter portion 74 is formed in a cylindrical shape extending in the axial direction DA, and is welded to the mounting member 61 in a state in which the end portion of the rear end side BE of the mounting member 61 is fitted in the opening of the end of the front end FE. Ru.

  The small diameter portion 75 is formed in a cylindrical shape that extends in the axial direction DA and has an outer diameter and an inner diameter smaller than the large diameter portion 74, and protrudes along the axial direction DA from the end of the rear end side BE in the large diameter portion 74 Is located in The small diameter portion 75 includes a reduced diameter portion 75 a formed in an annular shape extending inward in the radial direction at the end of the rear end side BE. An insertion port 75b for inserting the cable 13 is formed in the central region of the reduced diameter portion 75a.

  Inside the large diameter portion 74, the inner cylinder 33 and the inner cylinder connection fitting 34 are accommodated. Inside the small diameter portion 75, the outer cylinder connection fitting 64 and the grommet 65 are housed in a stacked state in order from the front end side FE to the rear end side BE.

  The outer cylinder connection fitting 64 is a cylindrically formed stainless steel member in which the end of the rear end side BE is closed. At the end of the rear end side BE of the outer cylinder connection fitting 64, a plurality of insertion openings 64a for inserting the cable 13 are formed.

  The grommet 65 is a member made of a heat-resistant rubber formed in a cylindrical shape extending in the axial direction DA. The grommet 65 is formed with a plurality of through holes 65 a for inserting the cable 13.

  The grommet 65 is accommodated inside the small diameter portion 75 in a state where the outer peripheral surface of the grommet 65 presses the inner peripheral surface of the small diameter portion 75. Further, the outer cylinder connection fitting 64 and the small diameter portion 75 are integrally fixed by caulking the outer peripheral surface of the small diameter portion 75 radially inward. Thereby, the grommet 65 is fixed to the inside of the small diameter portion 75 in a state of closing the insertion port 75 b of the small diameter portion 75.

  The insulating spacer 23 is a cylindrical member made of alumina extending in the axial direction DA. The insulating spacer 23 includes a large diameter portion 81, a small diameter portion 82, a step portion 83, and an inclined portion 84.

  The large diameter portion 81 is formed in a cylindrical shape extending in the axial direction DA. The small diameter portion 82 extends in the axial direction DA and is formed in a cylindrical shape having an outer diameter and an inner diameter smaller than those of the large diameter portion 81, and is disposed closer to the tip end FE than the large diameter portion 81.

  The stepped portion 83 extends in the axial direction DA and is formed in a cylindrical shape having an outer diameter equal to the large diameter portion 81 and an inner diameter equal to the small diameter portion 82. The stepped portion 83 is disposed so as to protrude from the end portion of the large diameter portion 81 on the tip end side FE along the axial direction DA. As a result, at the connection portion between the large diameter portion 81 and the step portion 83, a step 83a that protrudes inward in the radial direction is formed.

  The inclined portion 84 is disposed between the step portion 83 and the small diameter portion 82, and is formed in a cylindrical shape having an inner diameter equal to that of the small diameter portion 82. In addition, the inclined portion 84 is formed such that the outer diameter gradually decreases as it goes from the connection portion with the step portion 83 to the connection portion with the small diameter portion 82.

  The insulating spacer 23 is accommodated in the through hole 71 a of the mounting bracket 61 in a state where the outer peripheral surface of the inclined portion 84 is in contact with the shelf 71 b of the mounting bracket 61. The insulating spacer 23 is formed so as to have a gas contact surface 23 a in contact with the exhaust gas at the end of the tip end side FE of the insulating spacer 23 by being accommodated inside the mounting bracket 61 as described above.

  The metal shell 31 is accommodated inside the insulating spacer 23 in a state where the flange portion 42 is supported by the step 83 a of the insulating spacer 23. Thus, the metal shell 31 is accommodated in the mounting member 61 in a state of being electrically insulated from the mounting member 61.

The insulating spacer 24 is a cylindrical member made of alumina extending in the axial direction DA. The insulating spacer 24 includes a large diameter portion 86 and a small diameter portion 87.
The large diameter portion 86 is formed in a cylindrical shape extending in the axial direction DA. The small diameter portion 87 extends in the axial direction DA and is formed in a cylindrical shape having an outer diameter smaller than that of the large diameter portion 86 and an inner diameter equal to that of the large diameter portion 86. The small diameter portion 87 is disposed so as to project from the end of the tip end side FE of the large diameter portion 86 along the axial direction DA. A groove 87 a extending in the circumferential direction is formed on the outer peripheral surface of the small diameter portion 87. A cylindrical heater connector 89 is disposed in the groove 87a.

  The insulating spacer 24 is disposed closer to the rear end BE than the insulating spacer 23 by inserting the small diameter portion 87 into the inside of the large diameter portion 81 of the insulating spacer 23. Thereby, the inner cylinder 33 and the mounting bracket 61 are electrically insulated. A wire packing 90 is disposed between the large diameter portion 86 of the insulating spacer 24 and the end of the rear end BE of the mounting bracket 61. The end portion of the rear end side BE of the mounting bracket 61 is crimped so as to press the insulating spacer 24 toward the front end side FE via the wire packing 90. Thus, the insulating spacers 23 and 24 are fixed to the inside of the mounting bracket 61.

  The cable 13 is provided with the electric wires 101, 102, 103, 104, and 105, as shown in FIG. The electric wire 101 is a triple coaxial cable, and includes a lead wire 101a, an inner outer conductor 101b, and an outer outer conductor 101c. The inner outer conductor 101b surrounds the lead wire 101a. The outer outer conductor 101c surrounds the periphery of the inner outer conductor 101b. The electric wire 102 is a triple coaxial cable, and includes a lead wire 102a, an inner outer conductor 102b, and an outer outer conductor 102c. The inner outer conductor 102b surrounds the lead wire 102a. The outer outer conductor 102c surrounds the periphery of the inner outer conductor 102b. The wires 103, 104, and 105 are single-core insulated wires, and include lead wires 103a, 104a, and 105a.

  The lead wire 101a, 102a, 103a, 104a is connected to the metal terminal 106, 107, 108, 109 at the end of the tip end side FE, respectively. The lead wires 101 a, 102 a, 103 a and 104 a are inserted into the inner cylinder 33. The metal terminal 106 is disposed inside the separator 26. The metal terminals 107, 108 and 109 are disposed inside the separator 27.

  The lead wire 105a is inserted into the outer cylinder 62 as shown in FIG. The end of the tip end side FE of the lead wire 105 a is connected to the heater connection fitting 89. The inner outer conductors 101 b and 102 b are electrically connected to the inner fitting 21 by being in contact with the inner fitting 34 at the insertion opening 34 a of the inner fitting 34. The outer outer conductors 101 c and 102 c are electrically connected to the outer fitting 22 by being in contact with the outer tube fitting 64 at the insertion opening 64 a of the outer tube fitting 64.

  The insulating spacer 23 is provided with a heat generating resistor 111 as shown in FIG. The heating resistor 111 is formed in a linear shape, and is embedded in the inside of the small diameter portion 82 in a meandering manner along the entire circumference of the small diameter portion 82. The insulating spacer 23 includes a heater terminal 112. The heater terminal 112 is formed on the entire outer peripheral surface of the inclined portion 84. Then, one end of the heating resistor 111 is connected to the heater terminal 112.

  The insulating spacer 23 is provided with a heater terminal 113 as shown in FIG. The heater terminal 113 is formed in an annular shape extending along the circumferential direction of the large diameter portion 81 on the inner circumferential surface of the large diameter portion 81. Then, the other end of the heating resistor 111 is connected to the heater terminal 113. In a state where the insulating spacer 23 and the insulating spacer 24 are fixed to the inside of the mounting bracket 61, the heater connector 89 disposed in the groove 87 a of the insulating spacer 24 contacts the heater terminal 113 of the insulating spacer 23.

  As shown in FIG. 6, the ceramic element 12 is formed in a plate shape extending in the axial direction DA by sequentially laminating the ceramic layers 121, 122, and 123. The ceramic element 12 further includes a discharge electrode body 124 sandwiched between the ceramic layer 121 and the ceramic layer 122.

  The ceramic layers 121, 122, and 123 are members made of alumina formed in a plate shape extending in the axial direction DA, as shown in FIG. The ceramic layer 121 has a shorter length along the axial direction DA than the ceramic layers 122 and 123. The ceramic layer 122 and the ceramic layer 123 have the same length along the axial direction DA.

  The discharge electrode body 124 includes a needle-like electrode portion 141 and a lead portion 142. The needle-like electrode portion 141 is a member made of platinum and formed in a needle shape extending in the axial direction DA. The lead portion 142 is a member made of tungsten formed in a long shape extending in the axial direction DA by pattern printing. The end of the rear end side BE of the needle electrode portion 141 is connected to the end of the front end FE of the lead portion 142.

The ceramic element 12 includes insulating covering layers 125 and 126, an auxiliary electrode body 127, and a heater 128 for the element.
The insulating covering layer 125 is a member made of alumina formed in the same rectangular shape as the ceramic layer 121 by printing. The insulating covering layer 126 is a member made of alumina formed in the same rectangular shape as the ceramic layers 122 and 123 by printing.

  The auxiliary electrode body 127 is an electrode formed in a thin film shape extending in the axial direction DA by pattern printing. The auxiliary electrode body 127 includes a rectangular auxiliary electrode portion 144 and an elongated lead portion 145 extending in the axial direction DA. The end of the rear end side BE of the auxiliary electrode portion 144 is connected to the end of the front end side FE of the lead portion 145.

  The element heater 128 is a member formed by pattern printing using platinum paste containing platinum as a main component and containing ceramic. The element heater 128 includes a heating resistor 147 and lead portions 148 and 149. The lead portion 148 is connected to one end of the heating resistor 147, and the lead portion 149 is connected to the other end of the heating resistor 147.

  The ceramic element 12 is formed on the ceramic layer 123 in the order of proximity to the ceramic layer 123. The element heater 128, the insulating covering layer 126, the auxiliary electrode body 127, the ceramic layer 122, the discharge electrode body 124, the insulating covering layer 125 and the ceramic layer 121 has a stacked structure. As shown in FIG. 6, in the discharge electrode body 124, a portion of the tip end side FE in the needle-like electrode portion 141 and a portion of the back end side BE in the lead portion 142 are covered with the insulating covering layer 125 and the ceramic layer 121. It is arranged not to be.

  A portion of the ceramic layers 121 and 122 exposed to the outside of the ceramic element 12 and protruding from the tip of the ceramic holder 43 housed inside the metal shell 31 toward the tip side FE contacts the exhaust gas. Gas contact surface 12a. Of the gas contact surface 12a, the periphery of the needle-like electrode portion 141 is the gas contact surface 12b in which the corona discharge by the needle-like electrode portion 141 is suppressed when the insulation property is lowered.

Further, as shown in FIG. 7, the ceramic element 12 includes the conduction pattern 131 and the electrode pads 132, 133 and 134.
The conductive pattern 131 is disposed between the insulating coating layer 126 and the ceramic layer 123 on the rear end side BE of the element heater 128. The electrode pads 132, 133 and 134 are disposed in close contact with each other on the surface of the ceramic layer 123 opposite to the surface facing the ceramic layer 122. The electrode pads 132, 133 and 134 are disposed at the end of the rear end BE of the ceramic element 12.

  The conductive pattern 131 is electrically connected to the lead portion 145 of the auxiliary electrode body 127 via a through hole 126 a formed at the end of the rear end side BE of the insulating coating layer 126. Furthermore, the conductive pattern 131 is electrically connected to the electrode pad 132 via the through hole conductor 123 a penetrating the ceramic layer 123.

  The electrode pad 133 is electrically connected to the lead portion 148 of the element heater 128 via the through hole conductor 123 b penetrating the ceramic layer 123. The electrode pad 134 is electrically connected to the lead portion 149 of the element heater 128 through the through hole conductor 123 c penetrating the ceramic layer 123.

  The end of the rear end side BE of the discharge electrode body 124 contacts the metal terminal 106. The electrode pad 132 contacts the metal terminal 107. The electrode pad 133 contacts the metal terminal 108. The electrode pad 134 contacts the metal terminal 109.

  As shown in FIG. 8, the sensor control device 1 includes an isolation transformer 161, an inner circuit case 162, an outer circuit case 163, an ion source power supply circuit 164, an auxiliary electrode power supply circuit 165, and a measurement control unit 166. Prepare.

  The insulating transformer 161 includes a primary side iron core 171, a secondary side iron core 172, a primary side coil 173, and secondary side coils 174 and 175. The primary side coil 173 is wound around the primary side iron core 171. Both ends of the primary coil 173 are connected to the measurement control unit 166. The secondary side coils 174 and 175 are wound around the secondary side iron core 172. Both ends of the secondary coil 174 are connected to the ion source power supply circuit 164. Both ends of the secondary coil 175 are connected to the auxiliary electrode power supply circuit 165.

  The inner circuit case 162 is a conductor that surrounds the ion source power supply circuit 164 and the auxiliary electrode power supply circuit 165. Inner circuit case 162 is connected to secondary side iron core 172, inner outer conductor 101b and inner outer conductor 102b.

  The outer circuit case 163 is a conductor that surrounds the inner circuit case 162 and the measurement control unit 166. The outer circuit case 163 is grounded. The outer circuit case 163 is connected to the primary side iron core 171, the outer outer conductor 101c and the outer outer conductor 102c.

  The ion source power supply circuit 164 outputs a high voltage generated at both ends of the secondary coil 174 when a current flows in the primary coil 173. The ion source power supply circuit 164 includes output ends 164a and 164b. The output end 164a is connected to the inner outer conductor 101b. The output end 164b is connected to the lead wire 101a. The potential of the output end 164b is higher than the potential of the output end 164a.

  The auxiliary electrode power supply circuit 165 outputs a high voltage generated at both ends of the secondary coil 175 when a current flows in the primary coil 173. The auxiliary electrode power supply circuit 165 includes output ends 165a and 165b. The output end 165a is connected to the inner outer conductor 102b. The output end 165b is connected to the lead wire 102a. Note that the potential of the output end 165 b is higher than the potential of the output end 165 a.

The measurement control unit 166 includes a current detection circuit 181, heater energization circuits 182 and 183, a microcomputer 184, and a regulator power supply 185.
The current detection circuit 181 includes input ends 181a and 181b and an output end 181c. The input end 181 a is connected to the inner circuit case 162. The input end 181 b is connected to the outer circuit case 163. The current detection circuit 181 detects the current flowing between the input end 181a and the input end 181b, and outputs a signal indicating the detection result from the output end 181c.

  The heater energizing circuit 182 includes output ends 182a and 182b. The output end 182a is connected to the lead 103a. The output end 182 b is connected to the outer circuit case 163. The heater energizing circuit 182 outputs a PWM signal to the element heater 128 by applying a PWM control voltage between the output end 182a and the output end 182b in accordance with an instruction from the microcomputer 184, thereby the element heater 128. Control the temperature of the PWM is an abbreviation for Pulse Width Modulation.

  The heater energizing circuit 183 includes output ends 183a and 183b. The output end 183a is connected to the lead wire 105a. The output end 183 b is connected to the outer circuit case 163 and to the lead wire 104 a. The heater energizing circuit 183 causes the heating resistor 111 to generate heat by applying a preset heater energizing voltage between the output end 183 a and the output end 183 b in accordance with an instruction from the microcomputer 184.

  The microcomputer 184 includes a CPU, a ROM, a RAM, a signal input / output unit, and the like. The various functions of the microcomputer are realized by the CPU executing a program stored in the non-transitional tangible storage medium. In this example, the ROM corresponds to the non-transitional tangible storage medium storing the program. Also, by executing this program, a method corresponding to the program is executed. Note that part or all of the functions executed by the CPU may be configured as hardware by one or more ICs and the like.

The regulator power supply 185 receives a voltage supply from the battery 8 installed outside the sensor control device 1 and generates a voltage for operating the sensor control device 1.
As shown in FIG. 9, in the outer protector 51, an opening 51a is formed at the end of the distal end side FE. Further, in the outer protector 51, a plurality of gas inlets 51b are formed on the front end side FE of the side surface. The inner protector 52 is arranged such that the end of the distal end side FE of the inner protector 52 protrudes from the opening 51 a of the outer protector 51 to the distal end side FE.

  In the inner protector 52, a gas discharge port 52a is formed at the end of the tip end side FE. Further, on the side surface of the inner protector 52, a plurality of gas inlets 52b are formed on the rear end side BE of the gas inlet 51b of the outer protector 51.

  When the exhaust gas flows in the exhaust pipe 6 as shown by the arrow L1, the flow velocity of the exhaust gas rises outside the gas outlet 52a of the inner protector 52, and a negative pressure is generated in the vicinity of the gas outlet 52a.

  Due to this negative pressure, the exhaust gas in the inner protector 52 is discharged from the gas outlet 52 a to the outside of the inner protector 52 as shown by arrows L 2, L 3, L 4. As a result, as indicated by arrows L5 and L6, the exhaust gas present in the vicinity of the gas inlet 51b of the outer protector 51 is sucked into the inside of the outer protector 51 through the gas inlet 51b. Furthermore, as indicated by arrows L7, L8, L9 and L10, the exhaust gas sucked into the outer protector 51 flows into the inner protector 52 through the gas inlet 52b.

  When a high voltage (for example, 1 to 2 kV) is applied to the needle-like electrode portion 141 of the discharge electrode body 124 by the ion source power supply circuit 164, corona discharge occurs between the needle-like electrode portion 141 and the inner protector 52. Occur. The corona discharge generates positive ions PI around the needle-like electrode portion 141.

  Further, when the exhaust gas flows in from the gas introduction port 52b, a flow of exhaust gas from the rear end side BE toward the front end side FE is generated inside the inner protector 52. As a result, the cation PI generated around the needle-like electrode portion 141 is adsorbed to the fine particles MP contained in the exhaust gas and is charged to generate charged fine particles.

  In addition, a voltage (for example, 100 to 200 V) set in advance is applied to the auxiliary electrode portion 144 of the auxiliary electrode body 127 by the auxiliary electrode power supply circuit 165. As a result, the cation PI, which is suspended without being adsorbed to the particulates MP in the exhaust gas, moves in a direction away from the auxiliary electrode portion 144 by the repulsive force acting on the auxiliary electrode portion 144. The positive ions PI moving in the direction away from the auxiliary electrode portion 144 are captured by the inner wall of the inner protector 52 serving as the cathode. On the other hand, due to the adsorption of the cation PI, the charged fine particles have a large mass compared to the cation PI, so the influence of the repulsive force acting on the auxiliary electrode portion 144 is small. Therefore, the charged particulates are discharged from the gas outlet 52a in accordance with the flow of the exhaust gas.

  The inner fitting 21 and the outer fitting 22 are mutually insulated by insulating spacers 23 and 24. That is, the outer fitting 22 is grounded via the outer outer conductors 101c and 102c, and the inner fitting 21 is held in the exhaust pipe 6 in a state of being insulated from the outer fitting 22 at the ground potential.

Here, a current corresponding to the flow of positive ions PI discharged to the outside of the particulate sensor 2 is a leakage current I _esc, and a current corresponding to the flow of positive ions PI captured by the inner metal fitting 21 is a capture current I _trp Then, the relationship shown in the following equation (1) is established.

I _in = I _dc + I _trp + I _esc (1)
Then, the discharge current I _dc and the capture current I _trp flow to the inner fitting 21, and the input current I _in is held at a constant value. The input current I _in is a current for generating positive ions PI by corona discharge.

For this reason, as shown in the following equation (2), the leakage current I _esc can be calculated by the difference between the input current I _in and the sum of the discharge current I _dc and the capture current I _trp .
I _esc = I _in − (I _dc + I _trp ) (2)
As shown in the above equation (2), in the inner bracket 21, a current smaller than the input current I _in by the leakage current I _esc flows, so the reference potential of the inner bracket 21 is lower than the reference potential of the outer bracket 22. with the decrease in the potential of the inner fitting 21, it flows compensation current I _c to compensate for this potential drop from the current detection circuit 181 to the inner fitting 21 through the inner outer conductor 102b. The compensation current I _c corresponds to the leakage current I _esc . In other words, the compensation current I _c (or the leakage current I _esc ) corresponds to the signal current flowing according to the amount of charged particles. Current detection circuit 181 measures the value of the compensation current _{I c,} the measured value of the compensation current _{I c,} the measured value of the leakage current _{I esc.} Then, the current detection circuit 181 outputs a leakage current signal indicating the measured value of the leakage current I _esc to the microcomputer 184.

The microcomputer 184 specifies the measurement value of the leakage current I _esc based on the leakage current signal input from the current detection circuit 181, and correspondence between the measurement value of the leakage current I _esc and the amount of particulates in the exhaust gas The amount of particulates in the exhaust gas is calculated using the indicated map or arithmetic expression. Here, the amount of particulates in the exhaust gas can be evaluated, for example, as an amount based on the surface area of the particulates, and can also be evaluated as an amount based on the mass of the particulates. Alternatively, the amount of particulates in the exhaust gas can also be evaluated as an amount based on the number of particulates in the unit volume of exhaust gas.

  Further, the microcomputer 184 generates particulates attached to the needle-like electrode portion 141 of the discharge electrode body 124 by causing the element heater 128 and the heating resistor 111 to generate heat, and particulates attached to the gas contact surface 23 a of the insulating spacer 23. Burn and remove.

The microcomputer 184 also executes sensor control processing.
Here, the procedure of the sensor control process will be described. This sensor control process is a process that is started immediately after the microcomputer 184 is started by turning on the key switch of the vehicle.

  When this sensor control process is executed, the CPU of the microcomputer 184 first performs initial setting necessary for detection of fine particles, the element heater 128 and the heating resistor 111 in S10 as shown in FIG. Perform the initialization necessary for energizing. Then, at S20, driving of the ceramic element 12 is started. Specifically, at least a high voltage is applied to the discharge electrode body 124 by the ion source power supply circuit 164, and a voltage is applied to the auxiliary electrode body 127 by the auxiliary electrode power supply circuit 165.

  Further, in S30, the heater for water removal is energized. Specifically, the element heater 128 is caused to generate heat by the heater energization circuit 182, and the heating resistor 111 is caused to generate heat by the heater energization circuit 183. Thereby, the temperature of the gas contact surface 23a of the insulating spacer 23 and the temperature of the gas contact surfaces 12a and 12b of the ceramic element 12 rise to a preset evaporation temperature (for example, 250 ° C.).

  Then, at S40, it is determined whether the direct injection gasoline engine 3 has been started. Here, when the direct injection gasoline engine 3 has not been started, the processing of S40 is repeated. On the other hand, when the direct injection gasoline engine 3 is started, it is determined in S50 whether or not the key switch of the vehicle is switched to the off position. Here, when the key switch of the vehicle is not switched to the off position, the particle detection process is executed in S60, and the process proceeds to S50. Specifically, in S60, the amount of particulates in the exhaust gas is calculated based on the leakage current signal input from the current detection circuit 181, and particulate amount information indicating the amount of particulates is transmitted to the engine ECU 4.

On the other hand, when the key switch of the vehicle is switched to the off position, the sensor control process is ended.
A graph G1 in FIG. 11 shows a time change of the current value detected by the current detection circuit 181 when the water removal heater is energized at the start of the direct injection gasoline engine 3. A graph G2 in FIG. 11 shows a time change of the current value detected by the current detection circuit 181 when the water removal heater is not energized when the direct injection gasoline engine 3 is started. Solid lines SL1 and SL2 in the graphs G1 and G2 indicate the current values detected by the current detection circuit 181. The broken lines DL1 and DL2 in the graphs G1 and G2 indicate the results of detection of the amount of particles by the analyzer.

  As shown by the graph G1 in FIG. 11, when the heater for water removal is energized when the direct injection gasoline engine 3 is started, the current detection circuit 181 accurately increases the amount of particulates immediately after the start of the engine. It can be detected.

  On the other hand, as shown by the graph G2 in FIG. 11, when the water removal heater is not energized at the start of the direct injection gasoline engine 3, the current value detected by the current detection circuit 181 is negative immediately after the engine start. As a result, the microcomputer 184 can not calculate the amount of particulates in the exhaust gas.

  The sensor control device 1 configured as described above is attached to the exhaust pipe 6 of the direct injection gasoline engine 3 and controls the particulate sensor 2 that detects the amount of particulates contained in the exhaust gas in the exhaust pipe 6.

  The particulate sensor 2 includes the inner fitting 21 and the ceramic element 12, the insulating spacer 23 and the ceramic layers 121 and 122, the heating resistor 111 and the element heater 128. Hereinafter, the inner fitting 21 and the ceramic element 12 are also referred to as a detection unit.

The inner fitting 21 and the ceramic element 12 (i.e., the detection unit) are configured to allow the exhaust gas to flow into the interior and charge particulates contained in the inflowed exhaust gas.
The insulating spacer 23 is formed with a gas contact surface 23a in contact with the exhaust gas, and when particulates adhere to the gas contact surface 23a, the detection performance of the detection unit is lowered. The ceramic layers 121 and 122 are formed with the gas contact surfaces 12a and 12b in contact with the exhaust gas, and when particulates adhere to the gas contact surfaces 12a and 12b, the detection performance of the detection unit decreases.

The heating resistor 111 heats at least a part of the gas contact surface 23a. The element heater 128 heats the gas contact surfaces 12a and 12b.
Further, the sensor control device 1 performs heating by the heating resistor 111 and the element heater 128 so that the gas contact surface 23a, 12a, 12b attains an evaporation temperature at which water evaporates when the direct injection gasoline engine 3 is started. Do. The sensor control device 1 calculates the amount of particles using the signal current (compensation current I _c ) flowing based on the amount of charged particles, and outputs particle amount information indicating the amount of particles.

  Thus, when the direct injection gasoline engine 3 is started, the sensor control device 1 heats the gas contact surfaces 23a, 12a, 12b such that the gas contact surfaces 23a, 12a, 12b become evaporation temperatures at which water evaporates. . For this reason, the sensor control device 1 evaporates the condensed water generated at the cold start of the direct injection gasoline engine 3 by the gas contact surfaces 23a, 12a, 12b, and heats the heating resistor 111 and the element heater 128. Act on condensed water to move the condensed water away from the gas contact surfaces 23a, 12a, 12b to suppress adhesion of the condensed water to the gas contact surfaces 23a, 12a, 12b. it can. That is, in the sensor control device 1, the gas contact surfaces 23a, 12a, 12b are the same as the fine particles adhere to the gas contact surfaces 23a, 12a, 12b to lower the insulation performance of the insulating spacer 23 and the ceramic layers 121, 122. It is possible to suppress the decrease in the insulation performance of the insulating spacer 23 and the ceramic layers 121 and 122 due to the adhesion of the condensed water, and to suppress the decrease in the detection performance of the detection unit. Thereby, the sensor control device 1 can detect the amount of particulates at the time of cold start of the direct injection gasoline engine 3.

  The evaporation temperature is 200 ° C. or more. As a result, the sensor control device 1 can further suppress adhesion of condensed water to the gas contact surfaces 23a, 12a, 12b by the thermophoretic force based on the heating of the heating resistor 111 and the element heater 128. The detection accuracy of the amount of particles can be improved.

  In addition, the detection unit includes a discharge electrode body 124 including a needle-like electrode unit 141 configured to generate ions by corona discharge, and causes the generated ions to be attached to particulates contained in the exhaust gas and charged. Configured Furthermore, the ceramic layers 121 and 122 cover the discharge electrode body 124 with the needle-like electrode portion 141 exposed, and the gas contact surface 12 b is around the needle-like electrode portion 141 in the ceramic layer 121 and 122.

  The sensor control device 1 configured in this manner heats the periphery of the needle electrode portion 141 such that the evaporation temperature at which water evaporates around the needle electrode portion 141 when the direct injection gasoline engine 3 starts. Do. Therefore, the sensor control device 1 can suppress the occurrence of a situation where the condensed water adheres to the needle-like electrode portion 141 and the needle-like electrode portion 141 can not generate corona discharge.

  The particulate sensor 2 further includes an inner fitting 21 and an outer fitting 22. The insulating spacer 23 is disposed between the inner fitting 21 and the outer fitting 22 to electrically connect the inner fitting 21 and the outer fitting 22. Insulate. The inner fitting 21 has a gas intake pipe 32 for taking in the exhaust gas inside, has a potential different from that of the exhaust pipe 6, and is included in the detection unit. The outer fitting 22 surrounds the inner fitting 21 and is attached to the exhaust pipe 6 so as to be electrically connected to the exhaust pipe 6.

  In the sensor control device 1 configured as described above, when the direct injection gasoline engine 3 is started, condensed water is present on the gas contact surface 23 a of the insulating spacer 23 disposed between the inner fitting 21 and the outer fitting 22. It adheres and it can suppress that the insulation performance of the insulation spacer 23 between the inner side fitting 21 and the outer side fitting 22 falls. As a result, in the sensor control device 1, occurrence of a situation where the detection performance of the detection unit is lowered due to the leak current flowing between the inner fitting 21 and the outer fitting 22 when the condensed water adheres to the gas contact surface 23a. Can be suppressed.

  In the embodiment described above, the sensor control device 1 corresponds to a particle detection device, the inner metal fitting 21 and the ceramic element 12 correspond to a detection unit, the insulating spacer 23 and the ceramic layers 121 and 122 correspond to an insulating member, and heat is generated. The resistor 111 and the element heater 128 correspond to a heating unit.

Moreover, S30 corresponds to the process as a heating execution part, S60 corresponds to the process as an information output part, and the needle electrode part 141 corresponds to a discharge part.
As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, As long as it belongs to the technical scope of this invention, a various form can be taken.

For example, in the above embodiment, the evaporation temperature is 250 ° C., but the evaporation temperature may be a temperature at which water evaporates, that is, 100 ° C. or more.
Moreover, in the said embodiment, the form which detects the amount of microparticles | fine-particles was shown by producing | generating ion by corona discharge. However, the method of detecting the amount of particles is not limited to such a form. For example, it is a particulate sensor having a detection unit in which a pair of cylindrical electrodes are disposed in a form of being insulated from each other by an insulating member while having a predetermined gap, and exhaust gas is allowed to flow between the pair of electrodes The particle sensor charges the particles by applying a high voltage between the pair of electrodes to generate charged particles, and moves the charged particles between the pair of electrodes to detect the amount of particles. The present invention may be applied to a particle detection device that controls Since such a particulate sensor has a specific configuration described in US Patent Publication No. US 2012/0312074 A1 and US Patent Publication No. US 2013/0219990 A1, further detailed description will be omitted. In this case, for example, an insulating member that insulates between a pair of electrodes may be heated.

  In the above embodiment, while the auxiliary electrode body 127 is provided on the ceramic element 12 and the auxiliary electrode power supply circuit 165 for energizing the auxiliary electrode body 127 in the sensor control device 1 is provided, these auxiliary electrode body 127 and auxiliary electrode The power supply circuit 165 may be omitted.

  Further, the function possessed by one component in the above embodiment may be shared by a plurality of components, or the function possessed by a plurality of components may be exhibited by one component. In addition, part of the configuration of the above embodiment may be omitted. In addition, at least a part of the configuration of the above-described embodiment may be added to or replaced with the configuration of the other above-described embodiment. In addition, all the aspects contained in the technical thought specified from the wording as described in a claim are an embodiment of this indication.

  In addition to the sensor control device 1 described above, various forms including a system having the sensor control device 1 as a component, a program for causing a computer to function as the sensor control device 1, a medium storing the program, a sensor control method, etc. This disclosure can also be realized.

  DESCRIPTION OF SYMBOLS 1 ... Sensor control apparatus, 2 ... Particle sensor, 3 ... Direct injection gasoline engine, 6 ... Exhaust pipe, 12 ... Ceramic element, 12b ... Gas contact surface, 21 ... Inner metal fitting, 23 ... Insulation spacer, 23a ... Gas contact surface, 111 ... Heating resistor, 121, 122 ... Ceramic layer, 128 ... Heater for element

Claims (4)

A particulate detection device attached to an exhaust pipe of a direct injection gasoline engine and controlling a particulate sensor that detects the amount of particulates contained in exhaust gas in the exhaust pipe,
The particle sensor is
A detection unit configured to generate charged particulates by charging the particulates contained in the exhaust gas flowing into the interior thereof;
An insulating member configured to form a gas contact surface in contact with the exhaust gas, and when the particulates adhere to the gas contact surface, the detection performance of the detection unit decreases;
A heating unit configured to heat at least a portion of the gas contact surface;
The particle detector is
A heating execution unit configured to perform heating by the heating unit so as to reach an evaporation temperature at which water is evaporated on the gas contact surface when the direct injection gasoline engine is started;
An information output unit configured to calculate an amount of the particles using a signal current flowing based on the charged particles, and to output particle amount information indicating the amount of the particles. The particulate matter detection device according to claim 1, wherein
The particulate matter detection device wherein the evaporation temperature is 200 ° C. or higher. The particulate matter detection device according to claim 1 or 2, wherein
The detection unit is
The discharge electrode assembly includes a discharge portion configured to generate ions by corona discharge, and the generated ions are configured to be attached to the fine particles contained in the exhaust gas and charged.
The insulating member covers the discharge electrode body in a state in which the discharge portion is exposed,
The particulate matter detection device, wherein the gas contact surface is a periphery of the discharge portion in the insulating member. The particulate matter detection device according to any one of claims 1 to 3, wherein
The particle sensor is
An inner metal fitting which has a gas intake pipe for taking in the exhaust gas inside, is set to a potential different from that of the exhaust pipe, and is included in the detection unit;
And an outer metal fitting that is attached to the exhaust pipe and is electrically connected to the exhaust pipe.
The said insulation member is a particle detection apparatus arrange | positioned between the said inner side metal fitting and the said outer side metal fitting, and electrically insulating the said inner side metal fitting and the said outer side metal fitting.

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