JP2019002804A - Fine particle sensor - Google Patents

Abstract

To provide a fine particle sensor capable of reducing the amount of floating ions which are discharged out of a gas intake pipe via a gas discharge port without providing any auxiliary electrode for assisting the collection of floating ions by the gas intake tube by imparting a repulsive force to the floating ion toward the gas intake pipe.SOLUTION: A fine particle sensor 10 has a collection member 40 which is disposed between the tip 110 s of a discharge electrode body 110 and a gas discharge port 45O in a gas intake pipe 45, which is connected to the gas intake pipe 45 and functions as the collecting potential. The collection member 40 has one or multiple permeable porous parts 41 and 42 and a fixing part 43 having no pore for fixing the collection member 40 to the gas intake pipe 45.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a particle sensor.

  In an internal combustion engine (for example, a diesel engine), the exhaust gas may contain fine particles such as soot. The exhaust gas containing such fine particles is purified by collecting the fine particles with a filter. Moreover, the particulates accumulated in the filter are burned and removed by raising the temperature of the filter as necessary. However, when a problem such as breakage of the filter occurs, unpurified exhaust gas is directly discharged downstream of the filter. Therefore, there is a need for a particulate sensor capable of detecting particulates in exhaust gas in order to directly measure the amount of particulates in exhaust gas or detect a filter failure.

  Such a fine particle sensor is disclosed in Patent Document 1, for example. The fine particle sensor of Patent Document 1 includes a cylindrical gas intake tube extending from the rear end side to the front end side in the axial direction, and a discharge electrode body that generates ions by air discharge. The gas intake pipe is located on the rear end side of the gas intake pipe and is located on the front end side of the gas intake pipe and the gas intake port for taking in the measurement gas containing fine particles into the gas intake pipe. A gas discharge port for discharging the gas to be measured to the outside of the gas intake pipe is provided. The discharge electrode body is located on the rear end side with respect to the gas discharge port. This fine particle sensor generates charged charged fine particles by attaching ions generated by air discharge to the fine particles contained in the gas to be measured inside the gas intake pipe, and the outside of the gas intake pipe through the gas discharge port. Using the signal current that flows in accordance with the amount of ions contained in the charged fine particles discharged into the gas, the fine particles in the gas to be measured are detected.

JP 2015-129712 A

  By the way, in the fine particle sensor of Patent Document 1, the gas intake tube is used as a collection potential, and is also used as a collection electrode for collecting floating ions not attached to the fine particles among ions generated by air discharge. In addition to the discharge electrode body, the fine particle sensor of Patent Document 1 is provided with an auxiliary electrode body that applies repulsive force toward the gas intake tube to the floating ions and assists the collection of the floating ions by the gas intake tube. . However, when providing an auxiliary electrode body, in addition to the auxiliary electrode body, it is necessary to provide a power supply circuit for supplying power to the auxiliary electrode body, a cable for connecting the power supply circuit and the auxiliary electrode body, etc. There has been a problem that the number of components of the fine particle sensor increases and the manufacturing cost of the fine particle sensor increases. Moreover, since the electric power supplied to an auxiliary electrode body is also required, the amount of electric power used in the fine particle sensor has been increased. For this reason, the inventor of the present application studied to omit the auxiliary electrode body from the fine particle sensor.

  However, when the auxiliary electrode body is omitted from the fine particle sensor, the floating ions are easily released to the outside of the gas intake pipe through the gas discharge port. Specifically, among the ions generated in the vicinity of the tip of the discharge electrode body, the floating ions not attached to the fine particles tend to flow toward the gas discharge port toward the tip in the axial direction. For this reason, the floating ions that reach the gas discharge port without colliding (adhering) to the gas intake pipe may increase, and the floating ions that cannot be collected by the gas intake pipe may increase. That is, there is a possibility that the amount of floating ions discharged to the outside of the gas intake pipe through the gas discharge port together with the charged fine particles may increase.

  The fine particle sensor described above detects fine particles in the gas to be measured using a signal current that flows according to the amount of ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port. When there are floating ions discharged to the outside of the gas intake pipe through the gas discharge port together with the charged fine particles, a signal current corresponding to the amount of ions obtained by adding the amount of floating ions to the amount of ions contained in the charged fine particles flows. Become. That is, the magnitude of the detected signal current is larger than the magnitude of the signal current flowing in accordance with the amount of ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port. It is shifted (offset) by the magnitude of the signal current that flows according to the amount of floating ions discharged to the outside of the intake pipe. Therefore, a detection error is generated by the amount of the signal current that flows in accordance with the amount of floating ions discharged to the outside of the gas intake pipe through the gas discharge port. For this reason, if the auxiliary electrode body is omitted from the particle sensor, the amount of floating ions discharged to the outside of the gas intake pipe through the gas discharge port is increased, which may reduce the accuracy of particle detection.

  The present invention has been made in view of the current situation, without providing an auxiliary electrode body that assists the collection of floating ions by the gas intake pipe by giving repulsive force toward the gas intake pipe to the floating ions, It is an object of the present invention to provide a fine particle sensor capable of reducing the amount of floating ions released from the inside of a gas intake pipe to the outside through a gas discharge port.

  One aspect of the present invention includes a cylindrical gas intake tube extending from the rear end side to the front end side in the axial direction, and a discharge electrode body that generates ions by air discharge, and the gas intake tube includes the gas A gas intake port, which is located on the rear end side of the intake pipe, takes in the gas to be measured containing fine particles into the gas intake pipe, and a gas intake port which is located on the front end side of the gas intake pipe. A gas discharge port for discharging to the outside of the inlet pipe, and the discharge electrode body is located on the rear end side with respect to the gas discharge port, and is generated by the air discharge inside the gas inlet pipe. The ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port are generated by attaching the ions to the fine particles contained in the gas to be measured. Signal flowing according to the amount of In the fine particle sensor that detects the fine particles in the gas to be measured using a flow, the gas intake tube is set to a collection potential, and collects floating ions that have not adhered to the fine particles among the ions. The fine particle sensor also serves as a pole, and the gas intake pipe does not have an auxiliary electrode body that assists the collection of the floating ions by the gas intake pipe by applying a repulsive force toward the gas intake pipe to the floating ions. And a collecting member disposed between the tip of the discharge electrode body and the gas discharge port in the inside of the gas intake pipe. Has one or a plurality of porous parts having air permeability, and a fixing part that does not have a hole and fixes the collection member inside the gas intake pipe, and the one or more porous parts In each of the porous parts, Holes included in the porous portion are both have a straight shape extending in the thickness direction of the porous section, and a fine particle sensor is equal in size.

  The fine particle sensor described above applies repulsive force toward the gas intake tube to the floating ions (the ions generated by the air discharge that have not adhered to the fine particles) to assist the collection of the floating ions by the gas intake tube. It does not have an auxiliary electrode body. Thus, by omitting the auxiliary electrode body, it is possible to omit a power supply circuit for supplying power to the auxiliary electrode body, a cable connecting the power supply circuit and the auxiliary electrode body, etc. This can be simplified and the manufacturing cost of the fine particle sensor can be reduced. Further, by omitting the auxiliary electrode body, it is possible to reduce the amount of power used in the particle sensor.

  Further, in the above-described fine particle sensor, the auxiliary electrode body is omitted, and a collecting member that is connected to the gas intake pipe and has a collection potential is provided inside the gas intake pipe. More specifically, the collection member is arranged between the tip of the discharge electrode body and the gas discharge port in the gas intake pipe. As a result, among the ions generated near the tip of the discharge electrode body, the floating ions that have not adhered to the fine particles flow toward the gas discharge port, so that the floating ions collide (attach) to the gas intake tube. Even if it is not possible, at least a part of the floating ions can collide (attach) to the collecting member and be collected by the collecting member.

  More specifically, in the above-described particulate sensor, as the collecting member, one or a plurality of porous portions having air permeability and a fixing portion having no holes, and the collecting member is fixed inside the gas intake pipe. A collecting member having a fixed portion is used. In such a collecting member, at least a part of the floating ions is collected in the meat part (metal part) forming the hole in the porous part, and the gas to be measured and the charged fine particles are passed through the hole in the porous part. Can flow to the outlet side. Thereby, the gas to be measured and the charged fine particles can be discharged (discharged) to the outside of the gas intake pipe through the gas discharge port while collecting at least a part of the floating ions by the collection member. In addition, since the collecting member is fixed to the inside of the gas intake pipe by the fixing portion having no hole, the collecting member can be firmly fixed to the inside of the gas intake pipe.

  As described above, in the fine particle sensor described above, the charged fine particles together with the charged fine particles are provided without providing an auxiliary electrode body that applies a repulsive force toward the floating gas to the gas intake tube and assists the collection of the floating ions by the gas intake tube. The amount of floating ions released from the inside of the intake pipe to the outside can be reduced. Thereby, in the above-mentioned particulate sensor, since the signal current which flows according to the quantity of the floating ion discharged from the inside of the gas intake pipe can be reduced, the precision of particulate detection can be improved.

  Moreover, in the fine particle sensor described above, in each of the one or more porous portions, the holes included in the porous portion all have a shape that extends straight in the thickness direction of the porous portion. That is, each of the holes in each porous portion has a shape that extends straight in the thickness direction of the porous portion. By forming the hole in the porous portion in such a shape, the gas to be measured and the charged fine particles can smoothly pass through the hole in the porous portion, and the fine particles contained in the gas to be measured are clogged in the hole in the porous portion. It becomes difficult.

  Furthermore, in each of the one or more porous portions, the pores included in the porous portion have the same size. That is, in each porous part, the size of the holes contained in the porous part is the same. Note that “the same size of the holes” means substantially the same size, and allows a slight difference in size (including substantially the same) such as a manufacturing error. In this way, by aligning the sizes of the holes in each porous part, the ease of flow of the gas to be measured (ease of passage) is the same in all the holes included in the porous part, and the gas to be measured etc. Can pass through the porous portion more smoothly.

  Therefore, in the above-described particle sensor, the gas to be measured is discharged well, and as a result, the response of the particle sensor can be improved.

  The size of the pores in the porous portion is set to a size that allows the fine particles contained in the gas to be measured to pass through. For example, the size of the pores in the porous portion (the length of one side in the case of a square hole and the diameter in the case of a circular hole) is 200 times or more and 5000 times or less the average particle diameter of the fine particles contained in the gas to be measured. It is preferable to be within the range. Moreover, it is preferable that the aperture ratio of a porous part shall be in the range of 20 to 60%. By doing this, while preventing the fine particles and charged fine particles contained in the gas to be measured from clogging the pores of the porous portion, floating ions are more appropriately applied to the meat portion (metal portion) that forms the pore in the porous portion. Can be collected. In the case of a collecting member having a plurality of porous portions, in at least one porous portion, the size and aperture ratio of the pores are in the above range, and in other porous portions that are not in the above range. It is preferable to make it larger than the maximum value within the above range.

In addition, as the porous portion of the collecting member, for example, a mesh portion (for example, a wire net) knitted in a mesh shape of a metal wire, or a porous metal material (for example, in the form of dots) formed in a metal material (for example, a dotted shape) , Punching metal). In addition, examples of the shape of the porous portion include a flat plate shape (flat mesh shape) and a cylindrical shape.
In addition, as the fixing portion of the collecting member, for example, a portion that fixes the collecting member inside the gas intake pipe while holding the porous portion (fixed to itself), and the outer peripheral surface of the fixing portion is the gas collecting portion. The thing fixed to the inner peripheral surface of a gas intake pipe (for example, welding or press fit) in the aspect which contacts the inner peripheral surface of an inlet pipe can be mentioned. In addition, the fixing part of the collection member may be formed separately from the porous part (separate member), or may be formed integrally with one of the porous parts (single member).

  Furthermore, in the fine particle sensor, the porous portion of the collecting member may be a fine particle sensor having a mesh portion in which a metal wire is knitted in a mesh shape.

  In the fine particle sensor described above, the porous portion of the collecting member has a mesh portion in which a metal wire is knitted in a mesh shape. In such a mesh part, floating ions are collided (attached) to the metal wire part to collect the floating ions in the metal wire part, and the gas to be measured is passed through the holes (mesh) of the mesh part. It can flow smoothly to the gas outlet side of the gas intake pipe.

The fine particle sensor described above includes not only those having only a mesh portion as a porous portion but also those having another porous portion in addition to the mesh portion.
Moreover, as a shape of a mesh part, flat shape (flat net shape), cylinder shape (cylinder net shape), etc. can be mentioned.

  Furthermore, in any one of the fine particle sensors, the porous portion of the collecting member has a first porous portion formed of a mesh portion obtained by knitting a metal wire in a mesh shape and a predetermined shape in which a plurality of holes are formed. A fine particle sensor having a second porous portion made of a metal plate is preferable.

  In the fine particle sensor described above, the porous portion of the collecting member includes a first porous portion made of a mesh portion obtained by knitting a metal wire in a mesh shape, and a second porous portion made of a metal plate having a predetermined shape in which a plurality of holes are formed. Part. In this collecting member, the floating ions can be collected in the metal wire portion by colliding (attaching) the floating ions with the metal wire portion in the first porous portion, and the metal plate in the second porous portion. Since floating ions can be collected also in this portion, the collection rate of floating ions can be increased. In addition, the gas to be measured and the like can be passed through the first porous part through the holes (mesh) of the first porous part, and through the second porous part through the holes of the second porous part. The gas to be measured can be smoothly flowed to the gas discharge port side of the gas intake pipe.

  In addition, as a shape of a 1st porous part, flat shape (flat net shape), a cylindrical shape (cylinder net shape), etc. can be mentioned. In addition, examples of the shape (predetermined shape) of the second porous portion include a flat plate shape (disc shape or flat plate shape), a cylindrical shape (a metal plate formed with a plurality of holes formed into a cylindrical shape), and the like. it can.

  Furthermore, in any one of the fine particle sensors, the gas discharge port is located at a distal end portion of the gas intake tube and opens in the axial direction, and the distal end of the discharge electrode body is connected to the gas intake tube And at least a part of the collection member is located inside a cylindrical region surrounded by a virtual cylinder extending from the outer periphery of the gas discharge port to the rear end side in the axial direction. A fine particle sensor disposed inside the cylindrical region may be used.

  In the fine particle sensor described above, the gas discharge port is located at the tip of the gas intake pipe and opens in the axial direction. In addition, the tip of the discharge electrode body is located inside the gas intake tube and inside the cylindrical region surrounded by a virtual cylinder extending from the outer periphery (periphery) of the gas discharge port to the rear end side in the axial direction. ing. In such a fine particle sensor, at least a part of the floating ions not attached to the fine particles among the ions generated in the vicinity of the tip of the discharge electrode body flow toward the gas discharge port toward the front end in the axial direction.

  On the other hand, in the fine particle sensor described above, at least a part of the collecting member is disposed inside the cylindrical region. As a result, even if the floating ions flowing toward the gas discharge port toward the front end in the axial direction cannot be collected by colliding (attaching) to the gas intake tube, the floating ions collide with the collecting member. (Attached) and collected by the collecting member. Therefore, in the fine particle sensor described above, the amount of floating ions released from the inside of the gas intake tube to the outside can be reduced without providing an auxiliary electrode body.

  Further, in any one of the fine particle sensors, the collection member includes a partition portion disposed so as to partition the internal space of the gas intake pipe between the tip of the discharge electrode body and the gas discharge port. A fine particle sensor is preferable.

  In the fine particle sensor described above, the collection member has a partition portion arranged to partition the internal space of the gas intake tube between the tip of the discharge electrode body and the gas discharge port. Thus, by arranging at least a part (partition part) of the collection member so as to partition the internal space of the gas intake pipe, the floating ions flowing toward the gas discharge port reach the gas discharge port. Before it does, it will reach the collecting member. For this reason, the probability that the floating ions collide with the collection member is increased, and the collection rate of the floating ions by the collection member can be increased.

  In addition, the whole collection member may be a partition part, and a part of collection member may be a partition part. The former is, for example, a collecting member having a flat plate-like (flat net-like) porous portion and a flat plate-like (flat plate-like) fixing portion joined to the surface of the porous portion, The thing fixed to the inner peripheral surface of a gas intake pipe in the aspect which an outer peripheral surface contacts the internal peripheral surface of a gas intake pipe (for example, welding or press injection) can be mentioned. The latter includes, for example, a collecting member having a bottomed cylindrical (bottomed tubular net-like) porous portion and a fixing portion for fixing the porous portion inside the gas intake pipe, The collecting member whose bottom part (ceiling part) is a partition part can be mentioned.

  Further, in any one of the fine particle sensors, the fine particle sensor is attached to a metal vent pipe having a ground potential through which the gas to be measured flows, and the gas intake pipe is different from the ground potential. The discharge potential is set to the collection potential, and the discharge electrode body is set to a discharge potential different from the ground potential and the collection potential to generate the air discharge between the gas intake pipe and the gas discharge port. Is disposed in the vent pipe, and the particulate sensor is configured to detect the collection potential and the ground potential in accordance with the amount of the ions released from the gas intake pipe into the vent pipe through the gas discharge port. A fine particle sensor that detects the amount of the fine particles in the gas to be measured using the signal current flowing between the two is preferably used.

  The fine particle sensor described above is used by being attached to a metal vent pipe having a ground potential (potential different from the collection potential) through which the gas to be measured flows. The discharge electrode body has a discharge potential different from the ground potential and the collection potential, and generates an air discharge between the discharge electrode body and the gas intake tube. Further, the gas discharge port of the gas intake pipe is disposed in the vent pipe. In this fine particle sensor, a signal current flowing between the collection potential and the ground potential is used in accordance with the amount of ions released from the inside of the gas intake pipe into the ventilation pipe through the gas discharge port, and the gas in the gas to be measured is used. Detect the amount of fine particles.

  Even in such a fine particle sensor, as described above, the amount of floating ions released from the inside of the gas intake pipe to the outside (inside the vent pipe) can be reduced without providing an auxiliary electrode body. The signal current that flows according to the amount of floating ions can be reduced. As a result, the magnitude of the detected signal current (measured value of the signal current) is determined according to the amount of ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port. Therefore, the accuracy of particle detection can be improved.

1 is a schematic view of a vehicle equipped with a particulate detection system according to Example 1. FIG. 1 is a longitudinal sectional view of a fine particle sensor according to Example 1. FIG. It is another longitudinal cross-sectional view of the particulate sensor. It is a disassembled perspective view of the particulate sensor. It is the J section enlarged view of FIG. It is the elements on larger scale of the 1st porous part (mesh part) of a collection member. It is a schematic diagram of a particulate detection system. It is a perspective view of the sensor element which comprises a particulate sensor. It is a disassembled perspective view of the sensor element. It is a figure explaining the particulate sensor concerning Example 1. FIG. It is the B section enlarged view of FIG. It is the C section enlarged view of FIG. It is a cross-sectional view of the protector (gas intake pipe) of the fine particle sensor. It is the H section enlarged view of FIG. It is a correlation diagram between the gas discharge speed and the magnitude of the signal current (offset). 6 is a plan view of a collecting member according to Example 2. FIG. It is FF sectional drawing of FIG. 6 is a partial enlarged cross-sectional view of a particle sensor according to Example 2. FIG. 6 is a plan view of a collecting member according to Example 3. FIG. It is GG sectional drawing of FIG. 6 is a partial enlarged cross-sectional view of a particle sensor according to Example 3. FIG. It is a top view of the collection member concerning other forms. It is KK sectional drawing of FIG.

Example 1
Hereinafter, Example 1 of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram of a vehicle AM equipped with a particulate detection system 1 according to a first embodiment. FIG. 2 is a longitudinal sectional view of the particle sensor 10 according to the first embodiment. FIG. 3 is another longitudinal cross-sectional view of the particle sensor 10 according to the first embodiment, and is a cross-sectional view taken at a position shifted by 90 ° around the axis AX. FIG. 4 is an exploded perspective view of the particle sensor 10. FIG. 5 is an enlarged view of a portion J in FIG. 4, and is an exploded perspective view of the collecting member 40 according to the first embodiment. FIG. 6 is a partially enlarged view of the bottom portion 41 b of the first porous portion 41 (mesh portion) of the collecting member 40. FIG. 7 is a schematic diagram of the particulate detection system 1. However, in FIG. 7, the control device 200 included in the particle detection system 1 is mainly illustrated, and only a part of the particle sensor 10 (such as the electric wire 165) is illustrated.

  As shown in FIG. 2, the side where the protector 45 (gas intake pipe) is disposed (downward in FIG. 2) in the axial direction GH (the direction in which the axis AX extends, the vertical direction in FIG. 2) of the particulate sensor 10. Is the front end side GS, and the side (upward in FIG. 2) from which the electric wire 165 and the like on the opposite side extends is the rear end side GK.

  As shown in FIG. 1, the particle detection system 1 (hereinafter also simply referred to as the system 1) includes a particle sensor 10 and a control device 200 that controls the particle sensor 10. The particulate sensor 10 is attached to an exhaust pipe EP (venting pipe) of an engine ENG (internal combustion engine) mounted on the vehicle AM, and particulates S such as soot in the exhaust gas EG (measured gas) flowing through the exhaust pipe EP. Is detected. Specifically, the particulate sensor 10 is fixed to a metal exhaust pipe EP, and a part of the tip side thereof is disposed in the exhaust pipe EP and exposed to the exhaust gas EG (see FIG. 2).

  The control device 200 is connected to the particle sensor 10 via electric wires 165, 167, and 168 (see FIGS. 1 and 7). Of the electric wires 165, 167, and 168, the electric wire 165 is a triple coaxial cable (triaxial cable), and the electric wires 167 and 168 are small-diameter, single-core insulated wires. Among these, the electric wire 165 includes a discharge potential lead wire 161 as a core wire (center conductor) (see FIGS. 4 and 7). Further, the electric wire 167 includes a first heater lead wire 163 as a core wire, and the electric wire 168 includes a second heater lead wire 164 as a core wire (see FIGS. 4 and 7).

  The control device 200 includes an ion source power supply circuit 210 and a measurement control circuit 220 as shown in FIG. Among these, the ion source power supply circuit 210 has a first output terminal 211 having a sensor GND potential SGND and a second output terminal 212 having a discharge potential PV2. The second output terminal 212 is connected to the discharge potential lead wire 161. The discharge potential PV2 is set to a positive high potential (for example, 1 to 2 kV) with reference to the sensor GND potential SGND. The ion source power supply circuit 210 constitutes a constant current power source that is feedback-controlled for its output current and autonomously maintains its effective value at a predetermined current value (for example, 5 μA). The ion source power supply circuit 210 outputs a discharge potential PV2 applied to a discharge electrode body 110 described later.

The measurement control circuit 220 includes a signal current detection circuit 230 and a heater energization circuit 226. Among these, the signal current detection circuit 230 has a first input terminal 231 and a second input terminal 232 that are set to the sensor GND potential SGND. The signal current detection circuit 230 detects the signal current Is flowing between the first input terminal 231 and the second input terminal 232. The sensor GND potential SGND is set higher than the chassis GND potential CGND (ground potential) by an offset voltage V _offset (specifically, 0.5 V). Therefore, the second input terminal 232 is set to a potential that is higher than the chassis GND potential CGND by an offset voltage V _offset (specifically, 0.5 V).

  The heater energization circuit 226 is a circuit that energizes a heater 130 of the sensor element 100 described later by PWM control. The heater energization circuit 226 has a first heater energization end 226 a connected to the first heater lead 163 and a second heater energization end 226 b connected to the second heater lead 164. Note that the second heater energization end 226b and the second heater lead wire 164 are electrically connected to the chassis GND potential CGND and set to the chassis GND potential CGND. The first heater energization end 226a and the first heater lead wire 163 are set to the first heater potential PVht with reference to the chassis GND potential CGND.

  The ion source power supply circuit 210 is surrounded by an inner circuit case 250 that is set to the sensor GND potential SGND. The first output terminal 211 of the ion source power supply circuit 210 and the first input terminal 231 of the signal current detection circuit 230 are connected to the inner circuit case 250.

  In the first embodiment, the inner circuit case 250 houses and surrounds the ion source power supply circuit 210 and the secondary iron core 271B of the insulating transformer 270, and the first output terminal 211 of the ion source power supply circuit 210. To the sensor GND potential SGND. Further, the first output end 211 of the ion source power supply circuit 210 is electrically connected to the inner outer conductor 165G1 which is the sensor GND potential SGND among the coaxial double outer conductors 165G of the electric wire 165.

  The insulation transformer 270 is configured such that the iron core 271 is separated into a primary iron core 271A wound around the primary coil 272 and a secondary iron core 271B wound around the power circuit coil 273. Of these, the primary iron core 271A is electrically connected to the chassis GND potential CGND. On the other hand, the secondary iron core 271B is electrically connected to the sensor GND potential SGND (the first output terminal 211 of the ion source power supply circuit 210).

  Further, the ion source power supply circuit 210, the inner circuit case 250, and the measurement control circuit 220 including the signal current detection circuit 230 and the heater energization circuit 226 are surrounded by the outer circuit case 260 that is set to the chassis GND potential CGND. . Further, the second input end 232 of the signal current detection circuit 230, the second heater energization end 226b of the heater energization circuit 226, and the primary side iron core 271A of the insulation transformer 270 are connected to the outer circuit case 260 and connected to the chassis GND. The potential is CGND.

  In the first embodiment, the outer circuit case 260 includes therein an ion source power supply circuit 210, an inner circuit case 250, a measurement control circuit 220 including a signal current detection circuit 230 and a heater energization circuit 226, and insulation. The primary side iron core 271A of the transformer 270 is accommodated and surrounded. Further, the outer circuit case 260 is electrically connected to the outer outer conductor 165G2 having the chassis GND potential CGND among the coaxial double outer conductors 165G of the electric wire 165.

  The measurement control circuit 220 includes a regulator power source PS. The regulator power supply PS is connected to an external battery BT mounted on the vehicle AM through the power supply wiring BC, and is driven by the battery BT. Further, the GND potential of the battery BT is made common to the chassis GND potential CGND. The measurement control circuit 220 includes a microprocessor 202, and can communicate with a control unit ECU that controls the internal combustion engine via a communication line CC. Thereby, signals such as the measurement result (the magnitude of the signal current Is) of the signal current detection circuit 230 described above can be transmitted to the control unit ECU.

  Further, part of the electric power input from the outside to the measurement control circuit 220 through the regulator power supply PS is distributed to the ion source power supply circuit 210 through the insulation transformer 270. In the isolation transformer 270, a primary coil 272 that forms part of the measurement control circuit 220, a power circuit coil 273 that forms part of the ion source power circuit 210, and an iron core 271 (primary iron core 271A, secondary The side iron cores 271B) are electrically insulated from each other. For this reason, while electric power can be distributed from the measurement control circuit 220 to the ion source power supply circuit 210, electrical insulation between them can be maintained.

Next, the fine particle sensor 10 will be described in detail.
As shown in FIGS. 2 and 3, the particle sensor 10 is configured such that the axial direction GH (the direction in which the axis AX extends, the vertical direction in FIG. 2) from the rear end side (upper side in FIG. 2) to the front end side (lower side in FIG. 2). ). The fine particle sensor 10 includes a sensor element 100 that generates ions CP by air discharge (specifically, corona discharge). The sensor element 100 has a plate shape extending in the axial direction GH. In addition, the fine particle sensor 10 includes a metal shell 50 that holds the sensor element 100 while being electrically insulated from the sensor element 100 and is set to the sensor GND potential SGND. In addition, a mounting bracket 90 is provided that surrounds and holds the metallic shell 50 and is attached to the exhaust pipe EP and has a chassis GND potential CGND while ensuring electrical insulation with the metallic shell 50.

  More specifically, the fine particle sensor 10 includes a cylindrical mounting bracket 90 on its front end side GS. The mounting bracket 90 has a flange portion 91 that bulges outward in the radial direction and forms an outer shape hexagon. Further, the mounting bracket 90 has a cylindrical wall portion 93 that surrounds the outer periphery of a protector 45 (gas intake pipe), which will be described later, at a position closer to the distal end GS than the flange portion 91. A male screw 93b for fixing the particulate sensor 10 to the exhaust pipe EP is formed on the outer periphery of the rear end side GK in the cylindrical wall portion 93. Accordingly, the particulate sensor 10 is attached to a metal mounting boss BO separately fixed to the exhaust pipe EP using the male screw 93b of the mounting bracket 90, and is attached to the exhaust pipe EP via the mounting boss BO. Fixed. For this reason, the mounting bracket 90 is set to the same chassis GND potential CGND as the exhaust pipe EP.

  Further, a metal-made cylindrical outer cylinder 95 is fixed to the rear end side GK of the mounting bracket 90. Specifically, the front end portion 95s of the outer cylinder 95 is fitted on the rear end portion 90k of the mounting bracket 90, and the rear end portion 90k of the mounting bracket 90 and the front end portion 95s of the outer cylinder 95 are laser welded. Thus, the mounting bracket 90 and the outer cylinder 95 are integrated.

  On the inner side in the radial direction of the mounting bracket 90, a cylindrical metal shell 50 and an inner cylinder 80 integrated therewith are disposed via an insulating spacer 60 made of an electrical insulating material. Along with these, a cylindrical sleeve 62 and an annular wire packing 63 are also arranged in the mounting bracket 90.

  Specifically, the metal shell 50 has a substantially cylindrical shape and has an annular flange portion 51 that bulges radially outward. The inner cylinder 80 is made of metal and has a cylindrical shape extending in the axial direction GH. Then, the front end portion 80s of the inner cylinder 80 is fitted on the rear end portion 50k of the main metal shell 50 so that the front end of the inner tube 80 abuts on the flange portion 51 of the main metal shell 50, and the rear end portion of the main metal shell 50 The metal shell 50 and the inner cylinder 80 are integrated with each other by laser welding the 50k and the tip 80s of the inner cylinder 80.

  Further, the flange portion 51 of the metal shell 50 is disposed in the mounting metal 90 in a state of being sandwiched between the insulating spacer 60 located on the front end side GS and the sleeve 62 located on the rear end side GK. Note that an annular packing 65 made of carbon graphite is interposed between the flange portion 51 of the metal shell 50 and the insulating spacer 60, so that the airtightness between the flange portion 51 of the metal shell 50 and the insulating spacer 60 is interposed. Is secured. In addition, an annular packing 66 made of carbon graphite is interposed between the insulating spacer 60 and the mounting bracket 90 to ensure airtightness between the insulating spacer 60 and the mounting bracket 90. A wire packing 63 is disposed between the rear end portion 90kk of the mounting bracket 90 and the sleeve 62, and the rear end portion 90kk of the mounting bracket 90 is bent and crimped radially inward.

  A cup-shaped metal cup 52 is disposed inside the metal shell 50. Further, a hole 52b is formed at the bottom of the metal cup 52, and the sensor element 100 is inserted into the hole 52b. Further, around the sensor element 100, a cylindrical ceramic holder 53 made of alumina and holding the sensor element 100 in order from the front end side GS to the rear end side GK, and a first powder formed by compressing talc powder A filling layer 54, a second powder filling layer 55, and a cylindrical ceramic sleeve 56 made of alumina are disposed. Among these, the ceramic holder 53 and the first powder filling layer 54 are located in the metal cup 52.

  Further, a caulking ring 57 is disposed between the rearmost end 50 kk of the metal shell 50 and the ceramic sleeve 56. The rearmost end 50 kk of the metal shell 50 is bent and crimped radially inward, and presses the ceramic sleeve 56 via the crimping ring 57. Thereby, the powder of the second powder filling layer 55 is compressed, the metal cup 52 and the ceramic sleeve 56 are fixed in the metal shell 50, and the sensor element 100 is also airtightly held by the metal shell 50.

  Further, a cylindrical protector 45 (gas intake pipe) made of stainless steel is fixed to the distal end portion 50s of the metal shell 50 in a manner that surrounds the distal end portion 100S of the sensor element 100 from the radially outer side. The protector 45 protects the sensor element 100 from water droplets and foreign matters, and guides the exhaust gas EG to the periphery of the distal end portion 100S of the sensor element 100. The protector 45 is fixed to the tip 50s of the metal shell 50 as follows. Specifically, the rear end portion 45k of the protector 45 is externally fitted to the front end portion 50s of the metal shell 50, and the front end portion 50s of the metal shell 50 and the rear end portion 45k of the protector 45 are laser-welded. Has been. The site | part of the front end side GS of the protector 45 becomes the taper-shaped taper part 45c which diameter-reduces as it goes to the front end side GS.

  On the rear end side GK of the protector 45, a plurality of gas inlets 45I are formed in a manner of being arranged at equal intervals in the circumferential direction (see FIGS. 2 and 4). Exhaust gas EG (gas to be measured) containing fine particles S is taken into the protector 45 through the gas inlet 45I. Further, a gas discharge port 45O for discharging the introduced exhaust gas EG (gas to be measured) is formed at the tip of the protector 45. The gas discharge port 45 </ b> O is a circular opening whose axis coincides with the axis AX of the particle sensor 10, and only one gas discharge port 45 </ b> O is provided at the tip of the protector 45. In addition, the rear end side cylindrical portion 45t of the protector 45 in which the gas intake port 45I is formed is surrounded by the cylindrical wall portion 93 of the mounting bracket 90 around the radial direction via an annular gap. Yes. Thereby, the outside of the gas intake port 45 </ b> I is covered with the cylindrical wall portion 93.

  Moreover, the collection member 40 is arrange | positioned between the front-end | tip 110s (refer FIG. 8) of the discharge electrode body 110 and the gas exhaust port 45O among the insides of the protector 45 (internal space K). As will be described later, the collection member 40 is connected to a protector 45 (gas intake pipe) to obtain a collection potential (in this embodiment 1, a potential equal to the sensor GND potential SGND), and together with the protector 45, floating ions CPF. Is collected (see FIG. 10).

  As shown in FIGS. 4 to 6 and FIGS. 11 to 12, the collection member 40 includes a first porous portion 41, a second porous portion 42, and a fixing portion 43. Among these, the 1st porous part 41 consists of a mesh part which knitted the metal wire 41A in mesh shape (lattice shape), and has comprised the bottomed cylindrical mesh shape. The first porous portion 41 includes a disc-net-like bottom portion 41b and a cylindrical mesh-like side portion 41c extending from the bottom portion 41b to the rear end side GK in the axial direction GH. Each of the holes 41d (mesh) included in the first porous portion 41 has a shape extending straight in the thickness direction of the first porous portion 41 (the direction perpendicular to the paper surface in FIG. 6), and has an equivalent size. It is. The first porous portion 41 is disposed inside the protector 45 such that the bottom portion 41b is perpendicular to the axis AX (that is, the direction in which the hole 41d extends coincides with the axis direction GH). 10-12, the 1st porous part 41 is simplified and shown in figure.

  The second porous portion 42 is made of a metal plate (specifically, punching metal) in which a plurality of circular holes are formed, and has a cylindrical shape. The second porous portion 42 includes a disc-shaped bottom portion 42b and a cylindrical side portion 42c extending from the bottom portion 42b to the rear end side GK in the axial direction GH. Each of the holes 42d included in the second porous portion 42 has a shape that extends straight in the thickness direction of the second porous portion 42 and has an equivalent size. The second porous portion 42 is disposed inside the protector 45 such that the bottom portion 42b is perpendicular to the axis AX (that is, the direction in which the holes 42d extend is aligned with the axis direction GH).

  Moreover, the fixing | fixed part 43 consists of metal plates, and has comprised the annular | circular shape of cross-sectional substantially U shape (refer FIGS. 11-12). The fixing portion 43 is not formed with a hole. In addition, in the collection member 40 of the present Example 1, the 2nd porous part 42 and the fixing | fixed part 43 are formed by one member, and comprise the porous body 44 with a fixing | fixed part. That is, the porous body 44 with the fixing portion has the second porous portion 42 and the fixing portion 43.

  The collecting member 40 having such a configuration is fixed to the inner peripheral surface 45d of the protector 45 in such a manner that the outer peripheral surface 43b of the fixing portion 43 contacts the inner peripheral surface 45d of the protector 45. Specifically, for example, the collecting member 40 can be fixed inside the protector 45 by welding the fixing portion 43 of the collecting member 40 and the protector 45. Or you may make it fix the collection member 40 inside the protector 45 by press-fitting the fixing | fixed part 43 of the collection member 40 inside the protector 45. FIG. In the first embodiment, since the collecting member 40 is fixed to the inside of the protector 45 by the fixing portion 43 having no hole, the collecting member 40 can be firmly fixed to the inside of the protector 45.

  The thickness (diameter D) of the metal wire 41A that is the skeleton of the first porous portion 41 is 100 μm. The size E (length of one side) of the hole 41d (mesh) of the first porous portion 41 is 140 μm (see FIG. 6). The opening ratio of the first porous portion 41 is 34%. Further, the size (diameter) of the hole 42d of the second porous portion 42 is 2.2 mm. The aperture ratio of the second porous portion 42 is 43%. Both the hole 41d of the first porous part 41 and the hole 42d of the second porous part 42 are sized to allow the fine particles S contained in the exhaust gas EG to pass through.

  Here, with reference to FIG. 10, the intake of the exhaust gas EG into the protector 45 and the discharge of the exhaust gas EG to the outside of the protector 45 when the particulate sensor 10 is used will be described. In FIG. 10, the exhaust gas EG circulates in the exhaust pipe EP from left to right. When the exhaust gas EG flowing through the exhaust pipe EP passes around the taper portion 45c of the protector 45 of the particulate sensor 10, the flow velocity increases outside the gas discharge port 45O of the protector 45, and due to the venturi effect, A negative pressure is generated in the vicinity of the gas outlet 45O.

  Then, the intake exhaust gas EGI taken into the protector 45 is discharged from the gas discharge port 45O by this negative pressure. At the same time, the exhaust gas EG around the front end side cylindrical portion 45m of the protector 45 is taken into the space between the cylindrical wall portion 93 of the mounting bracket 90 and the rear end side cylindrical portion 45t of the protector 45, Further, the air is taken into the protector 45 through the gas inlet 45I of the protector 45. Since the intake exhaust gas EGI inside the protector 45 is discharged from the gas discharge port 45O to the outside of the protector 45, the protector 45 has a gas intake port 45I on the rear end side GK and a front end side GS on the inside of the protector 45. An air flow of the intake exhaust gas EGI flowing toward the gas discharge port 45O is generated.

  Incidentally, a collecting member 40 is disposed inside the protector 45. The collection member 40 has a first porous portion 41 and a second porous portion 42 that have air permeability (through which exhaust gas EG can pass). Accordingly, the intake exhaust gas EGI passes through the inside of the collecting member 40 through the hole 41d of the first porous portion 41 and the hole 42d of the second porous portion 42, and then reaches the gas discharge port 45O.

  As described above, in the particulate sensor 10 according to the first embodiment, a part of the exhaust gas EG flowing through the exhaust pipe EP is taken into the protector 45 through the gas intake port 45I and also taken into the protector 45. The exhaust gas EG (intake exhaust gas EGI) passes through the collection member 40 and is then discharged to the outside of the protector 45 through the gas discharge port 45O.

  In the fine particle sensor 10 of the first embodiment, as shown in FIG. 2, the rear end side GK of the metal shell 50 (specifically, the rear end side GK of the ceramic sleeve 56) is arranged inside the inner cylinder 80. Is provided with a ring-shaped insulating holder 173 made of an electric insulating material. The insulating holder 173 is formed with an insertion hole 173c penetrating the insulating holder 173 in the axial direction GH, and the sensor element 100 is inserted into the insertion hole 173c. Furthermore, a third insulating member 172 is disposed adjacent to the insulating holder 173 on the rear end side GK of the insulating holder 173. The third insulating member 172 is made of an electrical insulating material and has a cylindrical shape extending in the axial direction GH.

  Furthermore, a first insulating member 71 is disposed inside the third insulating member 172. The first insulating member 71 is made of an electrical insulating material and has a cylindrical shape extending in the axial direction GH. Further, a second insulating member 72 is disposed on the rear end side GK of the first insulating member 71. The second insulating member 72 is made of an electrical insulating material and has a cylindrical shape extending in the axial direction GH. A cylindrical spacer 78 extending in the axial direction GH is interposed between the first insulating member 71 and the second insulating member 72.

  The first insulating member 71 has an insertion hole 71c that penetrates itself in the axial direction GH. The sensor element 100 is inserted into the insertion hole 71c, and the discharge potential terminal member 73 is accommodated. Further, the second insulating member 72 has a first insertion hole 72c and a second insertion hole 72d that pass through the second insulating member 72 in the axial direction GH (see FIG. 4). Among these, the rear end portion 100K of the sensor element 100 is located in the second insertion hole 72d, and a first heater terminal member 76 and a second heater terminal member 77, which will be described later, are accommodated in an insulated state. ing.

  The first insulating member 71 holds the discharge potential terminal member 73 while bringing the discharge potential terminal member 73 into contact with the discharge potential pad 113 (see FIG. 8) of the sensor element 100 in the insertion hole 71c. Yes. At the same time, the first insulating member 71 electrically insulates the discharge potential terminal member 73 from the inner cylinder 80.

  Further, the second insulating member 72 holds the first heater terminal member 76 while bringing the first heater terminal member 76 into contact with the first heater pad 136 of the sensor element 100 in the second insertion hole 72d. Yes. Further, the second insulating member 72 holds the second heater terminal member 77 while bringing the second heater terminal member 77 into contact with the second heater pad 137 of the sensor element 100 in the second insertion hole 72d. Yes. At the same time, the second insulating member 72 electrically connects the first heater terminal member 76 and the second heater terminal member 77 to the sensor GND connection fitting 82 (a cylindrical member connected to the rear end portion 80k of the inner cylinder 80). Insulated.

  The discharge potential lead wire 161 is inserted into the first insertion hole 72 c of the second insulating member 72. One end portion 161 t of the discharge potential lead wire 161 is connected to the discharge potential terminal member 73. Thereby, the discharge potential terminal member 73 is set to the discharge potential PV2, and the discharge potential pad 113 connected to the discharge potential terminal member 73 is also set to the discharge potential PV2.

Further, the first heater terminal member 76 is connected to one end 163t of the first heater lead wire 163 in the second insertion hole 72d. As a result, the first heater terminal member 76 is set to the first heater potential PVht, and the first heater pad 136 connected to the first heater terminal member 76 is also set to the first heater potential PVht.
Further, the second heater terminal member 77 is connected to one end 164t of the second heater lead 164 in the second insertion hole 72d. Thus, the second heater terminal member 77 is set to the chassis GND potential CGND, and the second heater pad 137 connected to the second heater terminal member 77 is also set to the chassis GND potential CGND.

  The rear end portion 80k of the inner cylinder 80 is fitted with a tip end portion 82s of a sensor GND connection fitting 82 having a cylindrical shape and is laser-welded. The sensor GND connection fitting 82 is provided around the first insulating member 71 and the second insulating member 72 (more specifically, the third insulating member that houses and holds the first insulating member 71 and the second insulating member 72 therein). The periphery of the member 172 is surrounded. The rear end portion 82k of the sensor GND connection fitting 82 is caulked on the inner side in the radial direction, and supports the second insulating member 72 located on the inner side in the radial direction.

  Further, the outer outer conductor 165G1 of the outer conductor 165G of the electric wire 165 is electrically connected to the sensor GND connection fitting 82 through the first connection member 99. As shown in FIG. 4, the first connection member 99 has a grip portion 99b for inserting and gripping the external conductor 165G1, and an extending portion 99c extending from the grip portion 99b to the distal end GS (see FIG. 4). The grip portion 99b includes a cylindrical portion 99d having a substantially cylindrical shape in which a part in the circumferential direction is interrupted, and a pair of flat plate portions 99f extending in parallel while being separated from a portion in which a part in the circumferential direction of the cylindrical portion 99d is interrupted. And have. The pair of flat plate portions 99f are formed with holes through which the shaft portion 98b of the rivet 98 is inserted. Therefore, in a state where the outer conductor 165G1 is inserted into the cylindrical portion 99d of the grip portion 99b, the shaft portion 98b of the rivet 98 inserted through the holes of the pair of flat plate portions 99f is caulked to tighten the pair of flat plate portions 99f. By (approaching), the cylindrical portion 99d can be brought into close contact with the outer conductor 165G1 while reducing the diameter. In this way, the outer conductor 165G1 can be gripped by the grip portion 99b.

  As described above, with the outer conductor 165G1 held by the holding portion 99b, the tip 99s of the extending portion 99c of the first connection member 99 is connected to the rear end 82k of the sensor GND connection fitting 82, The external conductor 165G1 is electrically connected to the sensor GND connection fitting 82. Accordingly, the inner cylinder 80, the metal shell 50, and the protector 45 that are electrically connected to the sensor GND connection fitting 82 are all set to the sensor GND potential SGND.

  Further, a metal cylinder 85 is fitted and welded inside the small diameter portion 96 on the rear end side GK in the outer cylinder 95. Further, a fluoro rubber grommet 84 is disposed inside the cylindrical body 85, and electric wires 165, 167, 168 are inserted through the through holes of the grommet 84. An O-ring 86 is interposed between the small diameter portion 96 of the outer cylinder 95 and the cylinder 85.

  Further, of the outer conductor 165G of the electric wire 165, the outer outer conductor 165G2 is electrically connected to the outer cylinder 95 through the grip member 89 and the third connection member 87. As shown in FIG. 4, the gripping member 89 is parallel to the cylindrical portion 89d having a substantially cylindrical shape in which a part in the circumferential direction is interrupted and a portion in which a part in the circumferential direction of the cylindrical portion 89d is interrupted. And a pair of flat plate portions 89f extending in the direction. The pair of flat plate portions 89f are formed with holes through which the shaft portion 88b of the rivet 88 is inserted.

  Further, as shown in FIG. 4, the third connection member 87 includes a flat plate-shaped contact portion 87 b that contacts the flat plate portion 89 f of the gripping member 89, and a flat plate-like extension that is bent and extended from both ends of the contact portion 87 b. Parts 87c and 87d. A hole through which the shaft portion 88b of the rivet 88 is inserted is formed in the contact portion 87b. The extending portions 87 c and 87 d are portions connected to the inner peripheral surface of the outer cylinder 95.

  Therefore, the outer conductor 165G2 is inserted into the cylindrical portion 89d of the gripping member 89, and the flat plate portion 89f of the gripping member 89 is in contact with the contact portion 87b of the third connection member 87. The shaft portion 88b of the rivet 88 inserted through the hole of the contact portion 87b is swaged, and the pair of flat plate portions 89f are tightened (approached), so that the cylindrical portion 89d is reduced in diameter and brought into close contact with the outer conductor 165G2. be able to. In this way, the external conductor 165G2 can be gripped by the gripping member 89, and the gripping member 89 can be connected (coupled) to the third connection member 87.

  The extending portions 87 c and 87 d of the third connecting member 87 are connected to the inner peripheral surface of the outer cylinder 95, so that the outer conductor 165 G 2 is electrically connected to the outer cylinder 95. As a result, the outer cylinder 95, the mounting bracket 90 that conducts to the outer cylinder 95, and the exhaust pipe EP are all set to the chassis GND potential CGND that is insulated from the sensor GND potential SGND. The chassis GND potential CGND is common to the GND potential of the battery BT (see FIG. 7) mounted on the vehicle AM, as described above.

  Next, the sensor element 100 will be described in detail. As shown in FIGS. 8 and 9, the sensor element 100 has a plate shape extending in the axial direction GH and includes a ceramic base 101 made of an electrical insulating material (specifically, alumina). In the ceramic substrate 101, a discharge electrode body 110 and a heater 130 are embedded and sintered integrally.

  More specifically, the ceramic base 101 has three ceramic layers 102, 103, and 104 made of alumina derived from an alumina green sheet, and the ceramic layers 102 and 103 are made of alumina formed by printing. An insulating coating layer 105 is interposed. A discharge electrode body 110 is disposed between the ceramic layer 102 and the insulating coating layer 105. Further, an insulating coating layer 106 made of alumina formed by printing is interposed between the ceramic layer 103 and the ceramic layer 104. A heater 130 is disposed between the insulating coating layer 106 and the ceramic layer 104. And these are integrated and the sensor element 100 is formed.

  The discharge electrode body 110 has a form extending in the axial direction GH. The discharge electrode body 110 includes a needle electrode portion 112 made of a platinum wire, and a lead portion 111 that conducts to the needle electrode portion 112. The lead portion 111 is formed on the other surface 102S2 of the ceramic layer 102 by pattern printing. Further, the lead portion 111 and the buried portion 112A on the rear end side GK of the needle electrode portion 112 are buried in the ceramic base 101 (specifically, between the ceramic layer 102 and the ceramic layer 103). ing. Further, the lead portion 111 is discharged from one end 102b of the ceramic layer 102 through the through-hole conductor formed in the through-hole 102h penetrating the ceramic layer 102 from the end portion 111b on the rear end side GK. Conductive to the potential pad 113.

  On the other hand, the tip-side GS portion of the needle-like electrode portion 112 is an exposed portion 112B that is exposed to the outside of the ceramic base 101 so as to protrude from the tip 101S of the ceramic base 101 to the tip-side GS (see FIG. 8). ). A portion of the exposed portion 112B on the distal end side GS is a tapered needle-shaped distal end portion 112S.

  A heater 130 is formed on one surface 104S1 of the ceramic layer 104 by pattern printing. The heater 130 includes a heat generating portion 131 disposed on the front end side GS of the sensor element 100 and two heater lead portions (first heater lead) that are connected to the heat generating portion 131 and extend to the rear end side GK of the sensor element 100. Part 132 and a second heater lead part 133). The heater 130 is formed on one surface 104S1 of the ceramic layer 104 and is covered with an insulating coating layer 106. Accordingly, the heater 130 (the heat generating portion 131, the first heater lead portion 132, and the second heater lead portion 133) is embedded in the ceramic base 101 (specifically, between the ceramic layer 103 and the ceramic layer 104). ing.

  The first heater lead portion 132 is formed on the other surface 104S2 of the ceramic layer 104 from the end portion 134 on the rear end side GK through a through-hole conductor formed in the through-hole 104h1 penetrating the ceramic layer 104. The first heater pad 136 is electrically connected. Further, the second heater lead portion 133 is formed on the other surface 104S2 of the ceramic layer 104 from the end portion 135 on the rear end side GK through a through-hole conductor formed in the through-hole 104h2 that penetrates the ceramic layer 104. The second heater pad 137 is conducted.

Next, the electrical function and operation of the particulate detection system 1 will be described.
The discharge electrode body 110 of the sensor element 100 is connected to the ion source power supply circuit 210 of the control device 200 through the discharge potential lead wire 161 (see FIG. 7). The heater 130 is connected to the heater energization circuit 226 of the control device 200 through the first and second heater lead wires 163 and 164.

  Further, the outer conductor 165G1 inside the electric wire 165 is connected to the first output terminal 211 of the ion source power supply circuit 210 in the control device 200, and is set to the sensor GND potential SGND. Further, the protector 45 disposed around the sensor element 100 via the sensor GND connection fitting 82 and the like that are electrically connected to the external conductor 165G1 is also set to the sensor GND potential SGND.

  Here, a positive high voltage (for example, 1 to 2 kV) discharge potential PV2 is output by the ion source power supply circuit 210, and the discharge electrode is discharged through the discharge potential lead wire 161, the discharge potential terminal member 73, and the discharge potential pad 113. A discharge potential PV <b> 2 is applied to the needle electrode part 112 of the body 110. Then, an air discharge (specifically, corona discharge) is generated between the exposed portion 112B of the needle electrode portion 112 and the protector 45 (gas intake tube) having the sensor GND potential SGND, and the exposed portion Ions CP (positive ions) are generated around 112B (particularly, near the tip 110s of the discharge electrode body 110) (see FIG. 10).

  As described above, the exhaust gas EG is taken into the protector 45 through the gas inlet 45I. Therefore, as shown in FIG. 10, the ions CP generated around the exposed portion 112B adhere to the fine particles S in the intake exhaust gas EGI, and become the charged fine particles SC in which the fine particles S are positively charged. As described above, since the air flow of the intake exhaust gas EGI from the rear end side GK to the front end side GS is generated inside the protector 45, the charged fine particles SC together with the intake exhaust gas EGI are gas outlets. It flows toward 45O and is discharged out of the protector 45 through the gas discharge port 45O. Therefore, the charged fine particles SC are discharged as fine particles containing discharged ions CPH from the inside of the protector 45 into the exhaust pipe EP through the gas discharge port 45O.

  In the present system 1, the signal current detection circuit 230 detects a signal (signal current Is) corresponding to the charge amount of the discharged ions CPH discharged from the gas discharge port 45O. The signal current Is flows between the sensor GND potential SGND (the potential of the protector 45 and the like) and the chassis GND potential CGND (the potential of the exhaust pipe EP and the like). Thereby, the amount (concentration) of the fine particles S contained in the exhaust gas EG can be detected.

  As described above, in the first embodiment, the protector 45 disposed around the sensor element 100 is set to the sensor GND potential SGND, and a corona discharge is generated between the protector 45 and the exposed portion 112B of the discharge electrode body 110. Let Further, this protector 45 is also used as a collecting electrode for collecting floating ions CPF. That is, in the first embodiment, the collection potential for collecting the floating ions CPF by the protector 45 (collection electrode) is equal to the sensor GND potential SGND.

  Further, in the present system 1, the heater 130 is energized through the first heater pad 136 and the second heater pad 137 by the heater energization circuit 226 of the measurement control circuit 220 of the control device 200 (the first heater pad 136 and the second heater pad 136). When a predetermined heater energizing voltage is applied between the heater pads 137), the heat generating portion 131 of the heater 130 generates heat, and the sensor element 100 can be heated. Thereby, the foreign material adhering to the sensor element 100 can be removed.

  In the first embodiment, as the heater energization voltage, a voltage obtained by pulse-controlling the direct current battery voltage (DC 12 V or 24 V) of the battery BT of the vehicle AM by the heater energization circuit 226 is applied. Specifically, the first heater potential PVht applied to the first heater pad 136 through the first heater lead wire 163 and the first heater terminal member 76 is the positive side obtained by pulse-controlling the battery voltage (DC 12V or 24V). Potential. Further, the second heater potential applied to the second heater pad 137 through the second heater lead wire 164 and the second heater terminal member 77 is the chassis GND potential CGND common to the GND potential of the battery BT (FIG. 7). reference).

  By the way, unlike the conventional fine particle sensor, the fine particle sensor 10 of the first embodiment gives an auxiliary force to the floating ion CPF toward the gas intake tube (protector) to assist the collection of the floating ion CPF by the gas intake tube. It does not have an electrode body. Thus, by omitting the auxiliary electrode body, it is possible to omit a power supply circuit for supplying power to the auxiliary electrode body, a cable connecting the power supply circuit and the auxiliary electrode body, etc. This can be simplified and the manufacturing cost of the fine particle sensor can be reduced. Further, by omitting the auxiliary electrode body, it is possible to reduce the amount of power used in the particle sensor.

  However, in the conventional fine particle sensor, when the auxiliary electrode body is omitted, the floating ions are easily released to the outside of the gas intake pipe through the gas discharge port. Specifically, among the ions generated in the vicinity of the tip of the discharge electrode body, the floating ions not attached to the fine particles tend to flow toward the gas discharge port toward the tip in the axial direction. For this reason, the floating ions that reach the gas discharge port without colliding (adhering) to the gas intake pipe may increase, and the floating ions that cannot be collected by the gas intake pipe may increase. That is, there is a possibility that the amount of floating ions discharged to the outside of the gas intake pipe through the gas discharge port with the charged fine particles increases.

  In addition, when there are floating ions discharged to the outside of the gas intake pipe through the gas discharge port together with the charged fine particles, a signal current corresponding to the amount of ions obtained by adding the amount of the floating ions to the amount of ions contained in the charged fine particles flows. It will be. That is, the magnitude of the detected signal current is larger than the magnitude of the signal current flowing in accordance with the amount of ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port. It is shifted (offset) by the magnitude of the signal current that flows according to the amount of floating ions discharged to the outside of the intake pipe. Therefore, a detection error is generated by the amount of the signal current that flows in accordance with the amount of floating ions discharged to the outside of the gas intake pipe through the gas discharge port. For this reason, in the conventional fine particle sensor, if the auxiliary electrode body is omitted, the amount of floating ions discharged to the outside of the gas intake tube through the gas discharge port may increase, and the accuracy of the fine particle detection may be lowered.

  On the other hand, in the particulate sensor 10 of the first embodiment, as described above, the collecting member 40 connected to the protector 45 (gas intake pipe) and used as the collecting potential (sensor GND potential SGND) is connected to the protector 45. Is provided inside. More specifically, the collection member 40 is disposed between the tip 110s of the discharge electrode body 110 and the gas discharge port 45O in the protector 45 (see FIGS. 10 to 12). Thus, when the floating ions CPF that have not adhered to the fine particles S out of the ions CP generated in the vicinity of the tip 110s of the discharge electrode body 110 flow toward the gas discharge port 45O, the floating ions CPF are moved to the protector. Even if it cannot collide (attach) to 45, at least a part of the floating ions CPF can collide (attach) to the collecting member 40 and be collected by the collecting member 40.

  More specifically, in the particulate sensor 10 of the first embodiment, the collection member 40 includes a first porous portion 41 and a second porous portion 42 having air permeability, and a fixed portion 43 having no holes. A collecting member 40 is used. Specifically, the first porous portion 41 includes a porous portion formed of a mesh portion in which metal wires 41A are knitted in a mesh shape (lattice shape) and has a bottomed cylindrical mesh shape (see FIG. 5). The second porous portion 42 is made of a metal plate (specifically, punching metal) having a plurality of circular holes, and has a cylindrical porous portion (see FIG. 5).

  In such a collecting member 40, the floating ions CPF collide (attach) to the flesh portion (metal wire 41A) of the first porous portion 41, whereby the floating ions CPF can be collected in the portion of the metal wire 41A. it can. Further, the floating ions CPF collide (attach) to the meat part (metal part) of the second porous part 42 made of a metal plate (specifically, punching metal), so that the meat of the second porous part 42 The floating ions CPF can also be collected in the part (metal part). Thus, in the collection member 40, since it is possible to collect the floating ions CPF in the two porous parts (the first porous part 41 and the second porous part 42), the collection of the floating ions CPF is performed. The rate can be increased.

  Moreover, the collection member 40 allows the exhaust gas EG (measured gas) and the charged fine particles SC to pass through the first porous portion 41 through the holes 41d (mesh) of the first porous portion 41, and Since the second porous part 42 can be passed through the hole 42d of the two porous part 42, the exhaust gas EG and the charged fine particles SC can be appropriately flowed to the gas outlet 45O side of the protector 45 (gas intake pipe). . Therefore, the exhaust gas EG and the charged fine particles SC are discharged (discharged) to the outside of the protector 45 through the gas discharge port 45O while collecting at least a part of the floating ions CPF flowing through the protector 45 by the collecting member 40. be able to.

  As described above, in the fine particle sensor 10 of the first embodiment, without providing an auxiliary electrode body that applies a repulsive force toward the protector 45 to the floating ions CPF and assists the collection of the floating ions CPF by the protector 45, The amount of floating ions CPF released from the inside of the protector 45 together with the charged fine particles SC to the outside can be reduced. Thereby, in the particulate sensor 10 of the first embodiment, the signal current Is flowing according to the amount of the floating ions CPF released from the inside of the protector 45 can be reduced, so that the accuracy of particulate detection is improved. be able to.

  The size E (the length of one side, see FIG. 6) of the holes 41d (mesh) of the first porous portion 41 (mesh portion) is 140 μm, and the average particle diameter of the fine particles S contained in the exhaust gas EG The size is about 1400 times (about 200 to 5000 times) of (= about 100 nm). Furthermore, the aperture ratio of the first porous portion 41 is set to 34% (within a range of 20 to 60%). By doing so, the floating ions CPF are caused to flow in the metal wire 41A of the first porous portion 41 while preventing the fine particles S and the charged fine particles SC contained in the exhaust gas EG from clogging the holes 41d of the first porous portion 41. It can be collected more appropriately.

  Further, in the fine particle sensor 10 of the first embodiment, all the holes 41d included in the first porous portion 41 have a shape that extends straight in the thickness direction of the first porous portion 41 (the direction perpendicular to the paper surface in FIG. 6). Has been. Furthermore, all of the holes 42 d included in the second porous portion 42 have a shape that extends straight in the thickness direction of the second porous portion 42. By making the holes of each porous part (the first porous part 41 and the second porous part 42) into such a shape, the exhaust gas EG and the charged fine particles SC can smoothly pass through the holes of each porous part. Can do. In addition, the fine particles S contained in the exhaust gas EG are less likely to clog the pores of the respective porous portions.

  Furthermore, all the holes 41d included in the first porous portion 41 have the same size. Furthermore, all of the holes 42d included in the second porous portion 42 have the same size. Note that “the same size of the holes” means substantially the same size, and allows a slight difference in size (including substantially the same) such as a manufacturing error. In this way, by aligning the size of the holes in each porous portion, the ease of flow (ease of passage) of the exhaust gas EG and the like is the same in all the holes included in the porous portion. The exhaust gas EG and the like can be passed more smoothly. Therefore, in the fine particle sensor 10 of the first embodiment, the exhaust gas EG and the like can be discharged well, and as a result, the responsiveness of the fine particle sensor 10 can be improved.

  By the way, in the particulate sensor 10 of the first embodiment, the gas discharge port 45O is located at the tip of the protector 45 (gas intake pipe) and opens in the axial direction GH. Further, the tip 110s of the discharge electrode body 110 is provided inside the protector 45 and the virtual cylinder T (in FIGS. 11 and 12) in which the outer periphery (periphery) of the gas discharge port 45O extends to the rear end side GK in the axial direction GH. It is located inside a cylindrical area TA surrounded by a two-dot chain line (see FIGS. 11 and 12). In such a fine particle sensor, at least a part of the floating ions CPF that have not adhered to the fine particles S among the ions CP generated in the vicinity of the tip 110s of the discharge electrode body 110 are directed in the axial direction GH toward the gas discharge port 45O. It flows to the tip side GS.

  On the other hand, in the particulate sensor 10 of the first embodiment, at least a part of the collecting member 40 (specifically, the center of the bottom 41b of the first porous part 41 and the center of the bottom 42b of the second porous part 42). Part) is arranged inside the cylindrical area TA. As a result, even if the floating ions CPF flowing toward the distal end GS in the axial direction GH toward the gas discharge port 45O cannot be collected by colliding (attaching) to the protector 45, the floating ions CPF are collected. The collection member 40 can be collided (attached) and collected by the collection member 40.

Furthermore, in the fine particle sensor 10 of the first embodiment, the collecting member 40 is a partition portion 40b disposed so as to partition the internal space K of the protector 45 between the tip 110s of the discharge electrode body 110 and the gas discharge port 45O. (See FIGS. 10 to 12). The partition 40 b is formed by the bottom 41 b of the first porous part 41 and the bottom 42 b of the second porous part 42.
By providing such a partition portion 40b, the floating ions CPF flowing toward the gas discharge port 45O reach the collection member 40 before reaching the gas discharge port 45O. For this reason, the probability that the floating ions CPF collide with the collection member 40 is increased, and the collection rate of the floating ions CPF by the collection member 40 can be increased.

  By the way, in the fine particle sensor 10 of the first embodiment, the entire gas inlet 45I of the protector 45 (gas intake pipe) is arranged on the rear end side GK (further after the exposed portion 112B) than the front end 110s of the discharge electrode body 110. It is arranged on the rear end side GK) from the end 112BK (see FIG. 10). For this reason, the ions CP generated around the exposed portion 112B by corona discharge (air discharge) easily adhere to the fine particles S contained in the exhaust gas EG taken into the protector 45 through the gas inlet 45I. The amount of floating ions CPF can be reduced.

  Furthermore, in the fine particle sensor 10 of the first embodiment, a guide body 45G is provided at the gas inlet 45I of the protector 45 as shown in FIGS. FIG. 13 is a cross-sectional view of the protector 45 taken at the position BB in FIG. FIG. 14 is an enlarged view of a portion H in FIG. The guide body 45G reduces the exhaust gas EG so that a swirl flow is generated in which the exhaust gas EG (measured gas) taken into the protector 45 through the gas inlet 45I swirls around the exposed portion 112B. It is configured to be guided to the inside of the protector 45.

  Specifically, for a part of the cylindrical side wall portion of the protector 45, a U-shape comprising two cuts extending in parallel to the circumferential direction and a cut extending in the axial direction GH connecting the two cuts. The guide body 45G is formed and the gas intake port 45I is formed by bending a portion surrounded by the cut (a portion to be the guide body 45G) and bending the portion inward in the radial direction of the protector 45 ( (See FIGS. 13 and 14). The guide body 45G extends from the side wall portion of the protector 45 in a direction orthogonal to the axial direction GH. In the first embodiment, the gas intake ports 45I (guide bodies 45G) are provided at eight positions at equal intervals in the circumferential direction of the protector 45.

  Accordingly, the guide body 45G guides the exhaust gas EG to the inside of the protector 45, and generates a swirling flow in which the exhaust gas EG taken into the protector 45 swirls around the exposed portion 112B. In this way, by generating the swirling flow of the exhaust gas EG swirling around the exposed portion 112B, the ions CP generated around the exposed portion 112B come into contact (attachment) with the fine particles S contained in the exhaust gas EG. Since an opportunity can be increased, many ions CP can be attached to the fine particles S. Thereby, the signal current Is flowing according to the amount of ions CP adhering to the fine particles S (charge amount of the discharged ions CPH) can be increased, and the sensitivity of the fine particle sensor 10 can be improved.

  Further, as described above, the fine particle sensor 10 of the first embodiment is disposed around the radial direction of the protector 45 (specifically, the rear end side tubular portion 45t in which the gas intake port 45I of the protector 45 is formed). A cylindrical wall portion 93 is provided to surround the annular gap. The outside of the gas inlet 45I (the radially outer side of the protector 45) is covered with the cylindrical wall portion 93 (see FIG. 10). That is, when the protector 45 is viewed from the outside in the radial direction (a direction orthogonal to the axial direction GH), the gas intake port 45I is disposed at a position where it is hidden behind the cylindrical wall portion 93 and cannot be seen. For this reason, when water (water droplets) scatters from the outside of the protector 45 toward the gas intake port 45I, the cylindrical wall portion 93 prevents the water (water droplets) from entering the gas intake port 45I. It becomes possible. Thereby, the said water (water droplet) becomes difficult to enter the inside of the protector 45 through the gas inlet 45I.

(Comparison test of released amount of floating ions)
Next, a comparison test of the amount of floating ions CPF released from the inside of the protector (gas intake pipe) to the outside through the gas discharge port 45O was performed on the fine particle sensor 10 of Example 1 and the fine particle sensor of Comparative Example 1. . The particle sensor of Comparative Example 1 is different from the particle sensor 10 of Example 1 only in that it does not have the collection member 40, and the others are the same.

  Specifically, first, the particulate sensor 10 is attached to a test exhaust pipe (venting pipe), and air that does not contain soot and other particulates is caused to flow through the exhaust pipe, so that a signal detected by the signal current detection circuit 230 is detected. The magnitude of the current Is is grasped. In this test, the flow velocity of the air discharged from the protector gas discharge port 45O (gas discharge speed) is varied by varying the flow velocity of the air flowing through the exhaust pipe, and the respective gas discharge speeds are different. The magnitude (pA) of the signal current Is was measured. The same measurement was performed for the fine particle sensor of Comparative Example 1.

  In this test, air that does not contain soot and other fine particles is flowed as the gas to be measured. Therefore, the ions CP generated by the corona discharge are all floating ions CPF, and the ions CP released from the gas outlet 45O of the protector are also the ions CP. , All become floating ions CPF. Therefore, a particle sensor with a larger signal current Is can be said to be a particle sensor with a larger amount of floating ions CPF released from the inside of the protector (gas intake pipe) to the outside through the gas outlet 45O. In other words, the fine particle sensor having a smaller signal current Is can collect more floating ions CPF inside the protector (gas intake pipe), and the amount of floating ions CPF released from the inside of the protector to the outside. It can be said that it is a fine particle sensor that can reduce the above.

  The magnitude of the signal current Is detected in this test is included as an offset amount (measurement error) in the signal current Is detected when the exhaust gas containing fine particles such as soot is measured as the measurement gas. It will be. Therefore, when the exhaust gas containing fine particles such as soot is measured as the measurement gas, the magnitude of the signal current flowing according to the amount of ions contained in the charged fine particles discharged to the outside of the gas intake pipe through the gas discharge port. On the other hand, the amount of offset is shifted by a certain amount (detection error occurs).

  The results of this test are shown in FIG. FIG. 15 is a correlation diagram between the gas discharge speed (the flow speed of the gas discharged from the gas discharge port 45O of the protector) and the magnitude of the signal current Is (offset). In FIG. 15, the data (measured values) of Example 1 are plotted with rhombuses, and the correlation lines created based on these plots are indicated with solid lines. Further, the data of Comparative Example 1 is plotted as a rectangle, and the correlation line created based on these plots is indicated by a broken line.

  As can be seen from FIG. 15, when the gas discharge rates are made equal, the signal current Is is smaller in the particle sensor 10 of Example 1 than in the particle sensor of Comparative Example 1. More specifically, when the gas discharge rates are made equal, the magnitude (offset amount) of the signal current Is detected by the particulate sensor 10 of Example 1 is the magnitude of the signal current Is of the particulate sensor of Comparative Example 1. 1/10 or less of the height (offset amount). From this test result, the particulate sensor 10 of Example 1 can collect more floating ions CPF inside the protector (gas intake pipe) than the particulate sensor of Comparative Example 1, and from the inside of the protector. It can be said that it is a fine particle sensor that can reduce the amount of floating ions CPF released to the outside.

  Therefore, in the fine particle sensor 10 of the first embodiment, the signal current Is flowing according to the amount of the floating ions CPF released from the inside of the gas intake pipe (protector 45) to the outside is reduced as compared with the fine particle sensor of the first comparative example. Therefore, it can be said that the accuracy of particle detection can be improved. That is, in the fine particle sensor 10 of the first embodiment, the magnitude of the detected signal current Is (measured value of the signal current Is) is determined based on the ions contained in the charged fine particles SC discharged to the outside of the protector 45 through the gas discharge port 45O. Since the magnitude of the signal current that flows according to the amount of CP can be approached, the accuracy of particle detection can be improved.

  The reason why the amount of floating ions CPF released from the inside of the protector 45 to the outside in the fine particle sensor 10 of the first embodiment can be reduced as compared with the fine particle sensor of the first comparative example is that of the fine particle of the first embodiment. In the sensor 10, unlike the fine particle sensor of Comparative Example 1, it is because a larger amount of floating ions CPF can be collected inside the protector 45 by providing the collection member 40 inside the protector 45. I can say that.

(Example 2)
Next, Embodiment 2 of the present invention will be described with reference to the drawings. The fine particle sensor 310 of the second embodiment is different from the fine particle sensor 10 of the first embodiment only in the collecting member, and the others are the same. For this reason, it demonstrates centering on a different point from Example 1, and abbreviate | omits or simplifies description about the same point here. FIG. 16 is a plan view of the collecting member 140 according to the second embodiment. 17 is a cross-sectional view taken along line FF in FIG. FIG. 18 is a partial enlarged cross-sectional view of the particle sensor 310 according to the second embodiment. In FIGS. 17 and 18, the porous portion 141 is shown in a simplified manner.

  As shown in FIGS. 16 and 17, the collecting member 140 according to the second embodiment fixes the porous portion 141, the holding portion 142 that holds the porous portion 141, and the collecting member 140 inside the protector 45. And a fixing portion 143. Among these, the porous part 141 consists of the mesh part which knitted the metal wire 141A in mesh shape, and has comprised the disk shape (disk network shape).

  The holding portion 142 is made of a metal plate and has an annular shape (annular plate shape) having a circular through hole 142d at the center thereof. The fixing portion 143 is made of a metal plate and has an annular shape (annular plate shape) adjacent to the outer periphery of the holding portion 142. The fixing portion 143 has no hole. Note that the holding portion 142 and the fixing portion 143 are formed of a single member and constitute a holding and fixing member 144. That is, the holding and fixing member 144 has the holding portion 142 and the fixing portion 143.

In the collecting member 140, the peripheral portion of the porous portion 141 is welded to the holding portion 142, so that the porous portion 141 is held (fixed) by the holding portion 142 (holding fixing member 144).
Note that each of the holes 141d (mesh) included in the porous portion 141 has a shape that extends straight in the thickness direction of the porous portion 141 (vertical direction in FIG. 17) and has the same size. As shown in FIG. 18, the porous portion 141 is disposed inside the protector 45 in a direction orthogonal to the axis AX (that is, with the direction in which the hole 141 d extends coincides with the axis direction GH).

  The collecting member 140 having such a configuration is fixed (for example, welded) to the inner peripheral surface 45d of the protector 45 such that the outer peripheral surface 143b of the fixing portion 143 contacts the inner peripheral surface 45d of the protector 45 ( (See FIG. 18). Thereby, the collection member 140 is connected to the protector 45 (gas intake pipe) and is set to the collection potential (sensor GND potential SGND). More specifically, the collecting member 140 is a partition portion arranged to partition the internal space K of the protector 45 between the tip 110s of the discharge electrode body 110 and the gas discharge port 45O.

  Accordingly, also in the second embodiment, as in the first embodiment, the floating ions CPF that have not adhered to the fine particles S among the ions CP generated in the vicinity of the tip 110s of the discharge electrode body 110 are directed toward the gas outlet 45O. Even when the floating ions CPF cannot collide (attach) to the protector 45 when flowing, at least a part of the floating ions CPF collide (attach) to the collecting member 140 to collect the collecting member. 140 can be collected.

  Specifically, in the collection member 140 of the second embodiment, the floating ions CPF collide (attach) to the meat portion (metal wire 141A) of the porous portion 141, so that the floating ions CPF are captured in the portion of the metal wire 141A. Can be collected. The floating ions CPF can also be collected by the collision (attachment) of the floating ions CPF with the holding and fixing member 144 (the holding portion 142 and the fixing portion 143).

  Moreover, the collection member 140 is configured to collect the exhaust gas EG (measured gas) and the charged fine particles SC through the through-hole 142d of the holding portion 142 and the hole 141d (mesh) of the porous portion 141. Therefore, the exhaust gas EG and the charged fine particles SC can be appropriately flowed to the gas discharge port 45O side of the protector 45 (gas intake pipe). Accordingly, in the second embodiment, as in the first embodiment, at least a part of the floating ions CPF flowing through the protector 45 is collected by the collecting member 140, and the exhaust gas EG and the charged fine particles SC are removed from the gas exhaust. It is possible to appropriately discharge (discharge) the outside of the protector 45 through the outlet 45O.

Example 3
Next, Embodiment 3 of the present invention will be described with reference to the drawings. The particle sensor 410 according to the third embodiment is different from the particle sensor 10 according to the first embodiment only in the collecting member, and the others are the same. For this reason, it demonstrates centering on a different point from Example 1, and abbreviate | omits or simplifies description about the same point here. FIG. 19 is a plan view of the collecting member 240 according to the third embodiment. 20 is a cross-sectional view taken along the line GG in FIG. FIG. 21 is a partial enlarged cross-sectional view of the particle sensor 410 according to the third embodiment. 20 and 21, the first porous portion 241 is shown in a simplified manner.

  As shown in FIGS. 19 and 20, the collecting member 240 according to the third embodiment is fixed for fixing the first porous portion 241, the second porous portion 242, and the collecting member 240 inside the protector 45. Part 243. Among these, the 1st porous part 241 consists of a mesh part which knitted the metal wire 241A in mesh shape, and has comprised the disk shape (disk network shape). The second porous portion 242 is made of a metal plate, and a plurality of holes 242d (through holes) are arranged in an annular shape. The fixing portion 243 is made of a metal plate and has an annular shape (annular plate shape) adjacent to the outer periphery of the second porous portion 242. No hole is formed in the fixing portion 243. In addition, the 2nd porous part 242 and the fixing | fixed part 243 are formed with one member, and comprise the porous body 244 with a fixing | fixed part. That is, the porous body 244 with the fixing part has the second porous part 242 and the fixing part 243.

  In this collection member 240, the first porous portion 241 is welded to the porous body 244 with a fixing portion (the metal portion of the second porous portion 242), so that the first porous portion 241 is fixed to the porous body 244 with a fixing portion (first 2 (metal portion of the porous portion 242). Note that each of the holes 241d (mesh) included in the first porous portion 241 has a shape that extends straight in the thickness direction (vertical direction in FIG. 20) of the first porous portion 241 and has an equivalent size. It is. In addition, all the holes 242d included in the second porous portion 242 have a shape that extends straight in the thickness direction of the second porous portion 242 (the vertical direction in FIG. 20), and have the same size. As shown in FIG. 21, the first porous portion 241 and the second porous portion 242 are oriented in a direction perpendicular to the axis AX (that is, the direction in which the holes 241d and 242d extend matches the axial direction GH), and the protector 45. Is placed inside.

  The collecting member 240 having such a configuration is fixed (for example, welded) to the inner peripheral surface 45d of the protector 45 such that the outer peripheral surface 243b of the fixing portion 243 contacts the inner peripheral surface 45d of the protector 45 ( FIG. 20). Thereby, the collection member 240 is connected to the protector 45 (gas intake pipe) and is set to the collection potential (sensor GND potential SGND). More specifically, the collection member 240 is a partition portion arranged to partition the internal space K of the protector 45 between the tip 110s of the discharge electrode body 110 and the gas discharge port 45O.

  Accordingly, also in the third embodiment, as in the first embodiment, the floating ions CPF that have not adhered to the fine particles S among the ions CP generated in the vicinity of the tip 110s of the discharge electrode body 110 are directed toward the gas outlet 45O. Even when the floating ions CPF cannot collide (attach) to the protector 45 when flowing, at least a part of the floating ions CPF collide (attach) to the collecting member 240 to collect the collecting member. 240 can be collected. Specifically, in the collection member 240 of the third embodiment, the floating ions CPF collide (attach) to the metal portion of the second porous portion 242 and the metal wire 241A of the first porous portion 241, so that The floating ion CPF can be collected.

  Moreover, the collecting member 240 collects the exhaust gas EG (gas to be measured) and the charged fine particles SC through the holes 242d of the second porous portion 242 and the holes 241d (mesh) of the first porous portion 241. Since the collecting member 240 can be passed, the exhaust gas EG and the charged fine particles SC can be appropriately flowed to the gas discharge port 45O side of the protector 45 (gas intake pipe). Accordingly, also in the third embodiment, as in the first embodiment, the exhaust gas EG and the charged fine particles SC are removed from the gas exhaust while collecting at least a part of the floating ions CPF flowing through the protector 45 by the collecting member 240. It is possible to appropriately discharge (discharge) the outside of the protector 45 through the outlet 45O.

  In the above, the present invention has been described with reference to the first to third embodiments. However, the present invention is not limited to the above-described embodiments, and it can be applied as appropriate without departing from the scope of the present invention. Nor.

  For example, in Examples 1-3, the collection members 40-240 which have the 1st porous parts 41-241 which consist of a mesh part which knit the metal wires 41A-241A in mesh shape as a porous part were illustrated. However, as shown in FIG. 22 and FIG. 23, the porous portion made of a porous metal body in which a plurality of holes are formed in a metal material without having a porous portion made of a mesh portion obtained by knitting a metal wire in a mesh shape as the porous portion. You may make it use the collection member 340 which has.

  Specifically, as shown in FIGS. 22 and 23, the collecting member 340 is formed of a porous metal plate (for example, punching metal) in which a plurality of holes 341d are formed in a dotted shape in the metal plate. The disc-shaped perforated portion 341 having a plurality of holes 341d and an annular fixing portion 343 having no adjacent holes around the perforated portion 341d. The collecting member 340 is fixed (for example, welded) to the inner peripheral surface 45d of the protector 45 so that the outer peripheral surface 343b of the fixing portion 343 is in contact with the inner peripheral surface 45d of the protector 45. The exhaust gas EG and the charged fine particles SC can be flowed to the gas discharge port 45O of the protector 45 through the hole 341d while collecting at least a part of the floating ions CPF that circulate.

  In Examples 1 to 3, a plate-shaped ceramic laminate in which a plurality of ceramic layers are laminated in the thickness direction is illustrated as the ceramic base 101 constituting the sensor element 100. However, as a ceramic substrate, a ceramic substrate formed into a shape such as a rectangular column shape, a hexagonal column shape, a columnar shape, a cylindrical shape in addition to a plate shape may be used. For example, as a columnar or cylindrical ceramic substrate, a ceramic laminate in which a plurality of ceramic layers are laminated in an annual ring shape, or one or a plurality of ceramic sheets are wound in a spiral shape so that a plurality of ceramic layers are radially arranged. Examples include stacked ceramic laminates.

  Moreover, in Examples 1-3, the cylindrical wall part 93 located in the front end side GS of the attachment metal fitting 90 is inserted in the exhaust pipe EP, and the gas intake pipe (protector 45) is formed by the cylindrical wall part 93. It was set as the form which surrounds the outer periphery of the rear end side cylindrical part 45t. However, the gas inlet pipe (the protector is not provided) without the cylindrical wall portion 93 surrounding the outer periphery of the rear end side cylindrical portion 45t of the protector 45 (without inserting the cylindrical wall portion 93 into the exhaust pipe EP). The cylindrical member surrounding the outer periphery of 45) may be fixed to the distal end portion 50s of the metal shell 50 together with the gas intake pipe (protector 45).

DESCRIPTION OF SYMBOLS 1 Fine particle detection system 10,310,410 Fine particle sensor 40 Collection member 40b Partition part 41,241 1st porous part (mesh part)
41A, 141A, 241A Metal wire 140, 240, 340 Collection member (partition part)
141 Porous part (mesh part)
341 Porous portion 42, 242 Second porous portion 43, 143, 243, 343 Fixed portion 41d, 42d, 141d, 241d, 242d, 341d Hole 45 protector (gas intake tube, collecting electrode)
45I Gas inlet 45O Gas outlet 50 Main metal fitting 80 Inner cylinder 90 Mounting metal fitting 95 Outer cylinder 100 Sensor element 101 Ceramic base body 110 Discharge electrode body 110s Discharge electrode body tip 112 Needle electrode section 130 Heater 200 Controller ENG Engine (Internal combustion) organ)
EG Exhaust gas (measured gas)
EP exhaust pipe (venting pipe)
CGND Chassis GND potential (ground potential)
SGND sensor GND potential (collection potential)
PV2 Discharge potential S Fine particle SC Charged fine particle CP Ion CPF Floating ion GH Axial direction GS Tip side (Axial direction tip side)
GK Rear end side (Axial rear end side)
Is Signal current K Internal space T of gas intake pipe Virtual cylinder TA Cylindrical area

Claims (6)

A cylindrical gas intake pipe extending from the rear end side in the axial direction to the front end side;
A discharge electrode body that generates ions by air discharge,
The gas intake pipe is
A gas intake port that is located on the rear end side of the gas intake pipe and takes in the gas to be measured containing fine particles into the gas intake pipe, and a gas intake port that is located on the front end side of the gas intake pipe A gas outlet for discharging to the outside of the gas intake pipe,
The discharge electrode body is located on the rear end side of the gas discharge port,
Inside the gas intake pipe, the ions generated by the air discharge are attached to the fine particles contained in the gas to be measured to generate charged charged fine particles, and the gas intake pipe is passed through the gas discharge port. In the fine particle sensor that detects the fine particles in the gas to be measured using a signal current that flows in accordance with the amount of the ions contained in the charged fine particles discharged to the outside,
The gas intake pipe has a collection potential, and serves also as a collection electrode for collecting floating ions that did not adhere to the fine particles among the ions,
The particulate sensor
Without having an auxiliary electrode body that gives repulsive force toward the gas intake tube to the floating ions and assists the collection of the floating ions by the gas intake tube,
The collector is connected to the gas intake pipe to be the collection potential, and has a collection member disposed between the tip of the discharge electrode body and the gas discharge port inside the gas intake pipe,
The collection member has one or more porous portions having air permeability, and a fixed portion that does not have a hole and fixes the collection member inside the gas intake pipe,
In each of the one or more porous portions, each of the pores included in the porous portion has a shape that extends straight in the thickness direction of the porous portion and has an equivalent size. The fine particle sensor according to claim 1,
The porous portion of the collecting member is a fine particle sensor having a mesh portion in which a metal wire is knitted in a mesh shape. The fine particle sensor according to claim 1 or 2,
The porous part of the collecting member has a first porous part made of a mesh part obtained by knitting a metal wire in a mesh shape and a second porous part made of a metal plate having a predetermined shape in which a plurality of holes are formed. Particle sensor. The fine particle sensor according to any one of claims 1 to 3,
The gas discharge port is located at a distal end portion of the gas intake pipe, and is open in the axial direction.
The tip of the discharge electrode body is
Located inside the cylindrical area surrounded by a virtual cylinder inside the gas intake pipe and extending the outer periphery of the gas outlet to the rear end side in the axial direction,
At least a part of the collecting member is a particulate sensor disposed inside the cylindrical region. The fine particle sensor according to any one of claims 1 to 4,
The fine particle sensor, wherein the collecting member has a partition portion arranged so as to partition the internal space of the gas intake pipe between the tip of the discharge electrode body and the gas discharge port. The fine particle sensor according to any one of claims 1 to 5,
The fine particle sensor is attached to a metal vent pipe having a ground potential through which the gas to be measured flows.
The gas intake pipe has the collection potential different from the ground potential,
The discharge electrode body has a discharge potential different from the ground potential and the collection potential, and generates the air discharge between the gas intake pipe,
The gas outlet is disposed in the vent pipe;
The particulate sensor uses the signal current flowing between the collection potential and the ground potential according to the amount of the ions released from the gas intake pipe into the vent pipe through the gas discharge port. A fine particle sensor for detecting the amount of the fine particles in the gas to be measured.

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