JP6397686B2 - Particle sensor - Google Patents

Description

  The present invention relates to a fine particle sensor including an inner metal fitting having a gas intake pipe including a gas intake port that is used by being attached to a metal ventilation pipe through which a measurement gas containing fine particles flows.

  2. Description of the Related Art Conventionally, there has been known a fine particle sensor that is used by being attached to a metal ventilation pipe and detects the amount of fine particles contained in a gas to be measured flowing through the ventilation pipe. For example, a fine particle sensor that is mounted on an exhaust pipe of an internal combustion engine (diesel engine, gasoline engine, etc.) and detects the amount of fine particles such as soot contained in exhaust gas. More specifically, there is a fine particle sensor that takes in an exhaust gas flowing through an exhaust pipe, attaches ions to the fine particles in the intake gas to form charged fine particles, and then discharges the exhaust gas together with the intake gas to the exhaust pipe.

  Such a particle sensor includes, for example, an inner metal fitting having a gas intake pipe, an outer metal fitting, and an insulating spacer. Among these, the inner metal fitting is a metal member having a first electric potential different from the ground electric potential and having a gas intake port for taking exhaust gas into the gas intake pipe. The outer metal fitting is a cylindrical member that surrounds the inner circumference of the inner metal fitting, is attached to the exhaust pipe, and has a ground potential. The insulating spacer is a cylindrical member that is interposed between the inner metal fitting and the outer metal fitting to electrically insulate them from each other. This insulating spacer has a form in which a part (gas contact portion) is exposed in the exhaust pipe and is in contact with the exhaust gas flowing in the exhaust pipe. Such a fine particle sensor is disclosed in Patent Document 1, for example.

JP 2012-220423 A

  However, as described above, since the gas contact portion of the insulating spacer is in contact with the exhaust gas flowing through the exhaust pipe, foreign matters (such as soot and water droplets) contained in the exhaust gas may adhere to the gas contact portion. is there. If such foreign matter adheres to the gas contact portion, the insulating property of the insulating spacer decreases, and the insulating property between the inner metal fitting that is set to the first potential and the outer metal fitting that is set to the ground potential is reduced. There is a possibility that the detection of the amount of fine particles contained in can not be properly performed.

  The present invention has been made in view of such a situation, and suppresses a decrease in insulating property of an insulating spacer interposed between an inner metal fitting having a gas intake pipe and an outer metal fitting, and the gas to be measured is It is an object of the present invention to provide a fine particle sensor capable of appropriately detecting the amount of contained fine particles.

  One aspect of the present invention for solving the above problem is that a gas to be measured including fine particles flows and is attached to a metal vent pipe having a ground potential, and has a first potential different from the ground potential, A fine particle sensor including an inner metal fitting having a gas intake pipe including a gas intake port for taking in the gas to be measured inside, the fine particle sensor having a cylindrical metal enclosure surrounding the radial circumference of the inner metal fitting, and the vent pipe A cylindrical outer metal fitting that is attached to the ground potential and interposed between the inner metal fitting and the outer metal fitting surrounding portion of the outer metal fitting to electrically insulate them from each other. A cylindrical insulating spacer having a gas contact portion in contact with the gas to be measured flowing in the pipe, and the metal enclosure surrounding portion of the outer metal fitting is more radial in the vent pipe than the gas contact portion of the insulating spacer Fine with a shape protruding to the inside It is a child sensor.

  In this fine particle sensor, the metal enclosure portion of the outer metal fitting has a form that protrudes to the inside in the radial direction of the vent pipe from the gas contact portion of the insulating spacer. When the metal enclosure surrounding portion of the outer metal fitting is in such a form, the gas to be measured flowing through the ventilation pipe does not directly hit the gas contact portion of the insulating spacer, so that the foreign substance (soot contained in the gas to be measured) is contained in the gas contact portion. And water droplets) can be suppressed. Therefore, in this fine particle sensor, it is possible to suppress a decrease in the insulating property of the insulating spacer interposed between the inner metal fitting having the gas intake pipe set to the first potential and the metal fitting surrounding portion of the outer metal fitting set to the ground potential. The amount of fine particles contained in the gas to be measured can be detected appropriately.

  As described above, the “insulating spacer” is a form having a portion (gas contact portion) that is in contact with the gas to be measured flowing in the ventilation pipe. Specifically, for example, a form in which a part or all of the “gas contact portion” is located on the radially inner side of the inner peripheral surface of the vent pipe can be mentioned. Alternatively, although the “gas contact portion” faces the inside of the vent pipe, the whole “gas contact portion” may be positioned radially outside the inner peripheral surface of the vent pipe.

  As described above, the “metal enclosure portion” of the outer metal fitting is a form that protrudes inward in the radial direction of the vent pipe from the gas contact portion of the insulating spacer. Specifically, it is located on the radially inner side of the ventilation pipe with respect to the gas contact portion of the insulating spacer, but may not reach the gas inlet of the gas inlet pipe, or the gas inlet of the gas inlet pipe It is good also as a form which is located in the radial inside of a vent pipe further than this gas intake.

  Further, in the fine particle sensor, the bracket surrounding portion of the outer metal fitting protrudes to the inside in the radial direction from the gas intake port of the gas intake pipe, and in the thickness direction of the gas intake pipe. A fine particle sensor having a gas introduction window in a form in which at least a part of the gas inlet can be visually recognized from the outside of the metal enclosure portion is preferable.

The amount of gas to be measured that is taken into the gas intake pipe from the gas inlet is easily affected by the flow velocity of the gas to be measured that flows through the vent pipe. For this reason, detection of the amount of fine particles contained in the gas to be measured is also easily affected by the flow velocity of the gas to be measured, and it is difficult to improve detection accuracy.
On the other hand, in the above-described particle sensor, the metal enclosure portion of the outer metal fitting protrudes radially inward from the gas intake port of the gas intake pipe. When the metal enclosure portion of the outer metal fitting has such a configuration, even when the flow velocity of the gas to be measured flowing through the vent pipe is greatly changed, the change in the flow velocity of the gas to be measured can be reduced in the vicinity of the gas inlet. For this reason, the change in the amount of the gas to be measured taken into the gas intake pipe from the gas inlet is also reduced, and the amount of the gas to be measured is stabilized. Therefore, in this particulate sensor, it becomes difficult to be influenced by the flow velocity of the gas to be measured flowing through the vent pipe, and the amount of particulate contained in the gas to be measured can be detected with high accuracy.

  On the other hand, the metal enclosure portion of the outer metal fitting has a gas introduction window in a form in which at least a part of the gas inlet can be visually recognized from the outside of the metal enclosure portion in the thickness direction of the gas intake pipe. For this reason, the gas to be measured flowing on the outside in the radial direction of the metal enclosure can be directly led to the gas intake through the gas introduction window, so that the gas to be measured flowing through the ventilation pipe can be immediately taken into the gas intake pipe. Can do. Therefore, the amount of fine particles in the gas to be measured can be detected with good responsiveness.

  Further, in the fine particle sensor, the gas introduction window of the metal fitting surrounding portion has a form in which the entire gas intake port can be visually recognized from the outside of the metal fitting surrounding portion in the thickness direction of the gas intake pipe. A fine particle sensor is preferable.

  In this fine particle sensor, the gas introduction window of the outer metal fitting is configured so that the entire gas inlet can be visually recognized from the outside of the metal enclosure surrounding portion in the thickness direction of the gas intake pipe. The measurement gas can be more reliably guided to the gas intake through the gas introduction window. For this reason, the gas to be measured can be taken into the gas intake pipe earlier, and the amount of fine particles in the gas to be measured can be detected with higher responsiveness.

  Further, in the fine particle sensor according to any one of the above, the ions generated by the air discharge are attached to the fine particles contained in the measurement gas introduced into the gas intake pipe to be charged. A fine particle sensor that generates the charged fine particles and detects the amount of the fine particles in the gas to be measured using a signal current flowing according to the amount of the charged fine particles between the first potential and the ground potential; Good.

  In this fine particle sensor, the amount of fine particles in the gas to be measured is detected using a signal current that flows according to the amount of charged fine particles described above, but the signal current of the fine particles is very small. On the other hand, in the present invention, it is possible to suppress a decrease in insulating property of the insulating spacer interposed between the inner metal fitting having the gas intake pipe set to the first potential and the metal fitting surrounding portion of the outer metal fitting set to the ground potential. Therefore, the leakage current between the first potential and the ground potential can be suppressed, and the amount of minute signal current flowing between them can be detected appropriately. Thus, the amount of fine particles contained in the gas to be measured can be detected appropriately.

1 is an explanatory diagram illustrating a schematic configuration of a particle detection system according to an embodiment. It is a top view in the state where the particulate sensor concerning an embodiment was attached to the exhaust pipe. It is a longitudinal section in the state where the particulate sensor concerning an embodiment was attached to an exhaust pipe. It is a longitudinal cross-sectional view in the vertical cross section orthogonal to the cross section of FIG. 3 in the state attached to the exhaust pipe of the particulate sensor which concerns on embodiment. It is a disassembled perspective view of the particulate sensor concerning an embodiment. It is explanatory drawing which shows typically the mode of taking in of the microparticles | fine-particles in the microparticle sensor which concerns on embodiment, charging and discharge | emission. It is a top view in the state where the particulate sensor concerning a comparative example was attached to the exhaust pipe. About Example and Comparative Example, the graph which shows the relationship between the flow velocity of the exhaust gas which distribute | circulates the inside of an exhaust pipe, the inflow amount of the exhaust gas taken in from a gas intake, and the outflow amount of the exhaust gas discharged | emitted from a gas exhaust port It is. It is a top view in the state where the particulate sensor concerning modification 1 was attached to the exhaust pipe. It is a top view in the state where the particulate sensor concerning modification 2 was attached to the exhaust pipe.

(Embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of a particle detection system 1 including a particle sensor 10. 2 to 5 show the particle sensor 10 according to the present embodiment. 2 to 4, the side (upward in the figure) on which the gas intake pipe 25 is disposed in the axial direction GH (up and down direction in the figure) of the particle sensor 10 is the tip side GS, and the opposite side thereof. The side from which the cable 160 extends (downward in the figure) is defined as the base end side GK.
The particulate detection system 1 detects the amount of particulate S (soot, etc.) contained in the exhaust gas (measured gas) EG flowing through the exhaust pipe (vent pipe) EP of the internal combustion engine (engine) ENG. The particulate detection system 1 is mainly composed of a particulate sensor 10 according to the present embodiment, a circuit unit 200, and a pumping pump 300 (see FIG. 1).

  First, the particle sensor 10 will be described (see FIGS. 1 to 5). The fine particle sensor 10 is attached to a metal exhaust pipe EP having a ground potential PVE. Specifically, the particulate sensor 10 is attached to an attachment portion EPT provided with an attachment opening EPO in the exhaust pipe EP, and a gas intake tube 25 that forms a tip side portion of the inner metal fitting 20 in the particulate sensor 10 is provided. It arrange | positions in the exhaust pipe EP through the attachment opening EPO. Then, ions CP are attached to the fine particles S in the intake gas EGI taken into the gas intake pipe 25 from the gas intake 53h to form charged fine particles SC, and together with the intake gas EGI, from the gas discharge port 63h to the exhaust pipe EP. Discharge. The fine particle sensor 10 includes an inner metal fitting 20 having a gas intake pipe 25, a needle electrode body 80, an auxiliary electrode body 90, an outer metal fitting 100, a first insulating spacer 140, a second insulating spacer 150, a cable 160, and the like. .

  Of these, the inner metal fitting 20 has an outer cylindrical shape and is made of metal. The inner metal fitting 20 is electrically connected to an inner circuit case 250 or the like having a first potential PV1 in a circuit unit 200 to be described later via a first potential wiring 166 of the cable 160, and is different from the ground potential PVE. One potential is PV1. The inner metal fitting 20 includes an inner cylinder 30, a pipe holder 40, a nozzle member 50, a mixed discharge member 60, and a lid member 70 in order from the proximal end side GK to the distal end side GS. Among these, the nozzle member 50, the mixed discharge member 60, and the lid member 70 constitute the gas intake pipe 25.

  The inner cylinder 30 is a cylindrical and stainless steel member extending in the axial direction GH. The inner cylinder 30 is externally fitted to a distal end portion 160 s of a cable 160 which will be described later, and is caulked and connected to a first potential wiring 166 of the cable 160. A cylindrical insulating separator 35 is held inside the inner cylinder 30. Of the separator 35, the four through holes excluding the central through hole 35h include a second potential wiring 161, an auxiliary potential wiring 162, a first heater connection wiring 163a, and a second heater connection wiring 163b of the cable 160 described later. Each is inserted. Further, a distal end portion 164s of an air pipe 164 of the cable 160, which will be described later, is opened on the proximal end side GK from the separator 35 in the inside of the inner cylinder 30.

  The pipe holder 40 is a stainless steel member extending in the axial direction GH. The pipe holder 40 is fitted and fixed to the distal end portion of the inner cylinder 30 and is electrically connected to the inner cylinder 30. The pipe holder 40 includes a columnar holding portion 41, a cylindrical tube wall portion 43 extending from the periphery of the holding portion 41 to the distal end GS, and an annular shape that bulges radially outward from the holding portion 41. It consists of a flange portion 45. Among these, the holding portion 41 is provided with a needle electrode insertion hole 41h, an auxiliary electrode insertion hole 41i, and a ventilation through hole 41j that penetrate in the axial direction GH. A needle-shaped electrode body 80 and a needle-shaped electrode insulating pipe 85 described later are inserted and held in the needle-shaped electrode insertion hole 41h. Further, an auxiliary electrode body 90 and an auxiliary electrode insulating pipe 95 described later are inserted and held in the auxiliary electrode insertion hole 41i. On the other hand, the ventilation through hole 41j communicates with the inside of the inner cylinder 30 on the base end side GK.

  The nozzle member 50 is a bottomed cylindrical stainless steel member extending in the axial direction GH. The nozzle member 50 is fitted into and fixed to the distal end portion of the cylindrical wall portion 43 of the pipe holder 40 and is electrically connected to the pipe holder 40. The nozzle member 50 includes a nozzle portion 51 located at the bottom thereof, and a cylindrical cylindrical wall portion 53 extending from the peripheral edge of the nozzle portion 51 to the distal end side GS. Among these, the nozzle part 51 is formed in a concave shape whose center is directed to the front end side GS, and a fine through hole is formed at the center to form a nozzle 51n. On the other hand, the cylindrical wall portion 53 is provided with a gas intake port 53h that opens toward the downstream side of the exhaust pipe EP. The gas inlet 53h is an opening (specifically, a circular hole) for taking the exhaust gas EG flowing through the exhaust pipe EP into the gas intake pipe 25.

  By fixing the nozzle member 50 to the pipe holder 40, a cylindrical discharge space is formed between the holding portion 41 of the pipe holder 40, the cylindrical wall portion 43 of the pipe holder 40, and the nozzle portion 51 of the nozzle member 50. DS is formed. In this discharge space DS, a needle-like tip portion 83 of a needle-like electrode body 80, which will be described later, protrudes toward the tip side GS and faces the opposing surface 51t that forms the concave shape of the nozzle portion 51.

  The mixed discharge member 60 is a stainless steel member extending in the axial direction GH. The mixed discharge member 60 is fitted and fixed to the distal end portion of the cylindrical wall portion 53 of the nozzle member 50 and is electrically connected to the nozzle member 50. The mixed discharge member 60 includes a base end portion 61 located on the base end side GK, and a cylindrical tube wall portion 63 extending from the periphery of the base end portion 61 to the front end side GS. Among these, the base end portion 61 is configured such that the radially inner space is narrowed in a slit shape by the collecting pole 62 bulging radially inward. The collecting electrode 62 is formed with a notch 62 c in accordance with the position of the gas inlet 53 h of the nozzle member 50. The notch 62c forms a lead-in passage HK that communicates from the gas inlet 53h to a cylindrical mixing region MX1 of the mixing region MX described later. On the other hand, the cylindrical wall portion 63 is provided with a gas discharge port 63h that opens toward the downstream side of the exhaust pipe EP. The gas discharge port 63h is an opening (specifically, a circular hole) for discharging the intake gas EGI and the air AR in the gas intake pipe 25 to the exhaust pipe EP. Further, the distal end portion of the cylindrical wall portion 63 is closed by being covered with a disc-shaped stainless steel lid member 70.

  By fixing the mixed discharge member 60 to the nozzle member 50, a cylindrical shape is formed between the nozzle portion 51 of the nozzle member 50, the cylindrical wall portion 53 of the nozzle member 50, and the base end portion 61 of the mixed discharge member 60. A cylindrical space that forms the mixing region MX1 is formed. On the other hand, the slit-shaped internal space formed by the collecting electrode 62 at the base end portion 61 of the mixed discharge member 60 forms a slit-shaped mixed region MX2, and the mixed region MX is formed by the cylindrical mixed region MX1 and the slit-shaped mixed region MX2. Is formed. An auxiliary electrode portion 93 of an auxiliary electrode body 90 to be described later protrudes toward the proximal end side GK in the slit-shaped mixed region MX2. Further, the columnar space between the base end portion 61 of the mixed discharge member 60, the cylindrical wall portion 63 of the mixed discharge member 60, and the lid member 70 forms a gas discharge path EX. This gas discharge path EX communicates with the slit-shaped mixing region MX2 of the mixing region MX. A bent portion 92 of an auxiliary electrode body 90, which will be described later, is disposed in the gas discharge path EX.

  Next, the needle electrode body 80 will be described. This acicular electrode body 80 is made of a tungsten wire, and has a straight rod-shaped extension portion 81 and a needle-shaped tip portion 83 that is located at the tip portion of the needle-shaped electrode portion and forms a needle-like second discharge electrode. Consists of. Among these, the base end portion of the extending portion 81 is connected to the second potential wiring 161 of the cable 160 described later in the separator 35. The extending portion 81 is covered with a cylindrical needle-shaped electrode insulating pipe 85 made of an insulating ceramic around the radial direction. The extending portion 81 of the needle electrode body 80 and the needle electrode insulating pipe 85 are inserted into the needle electrode insertion hole 41 h of the holding portion 41 of the pipe holder 40 and held by the holding portion 41. . On the other hand, the needle-like tip portion 83 of the needle-like electrode body 80 protrudes toward the tip side GS in the discharge space DS and faces the facing surface 51t of the nozzle portion 51 as described above.

  Next, the auxiliary electrode body 90 will be described. The auxiliary electrode body 90 is made of a stainless steel wire, and has a straight rod-like extension portion 91, a bent-back portion 92 bent back in a U shape at the distal end side GS, and the bent-back portion 92 to the proximal end side GK. The auxiliary electrode portion 93 has an auxiliary electrode that extends and has a pointed needle shape. Among these, the base end portion of the extending portion 91 is connected to an auxiliary potential wiring 162 of the cable 160 described later in the separator 35. The extension 91 is covered with an auxiliary electrode insulating pipe 95 with a heater. The extension portion 91 and the auxiliary electrode insulating pipe 95 of the auxiliary electrode body 90 are inserted into the auxiliary electrode insertion hole 41 i of the holding portion 41 of the pipe holder 40 and are held by the holding portion 41. On the other hand, the bent-back portion 92 is disposed in the gas discharge path EX as described above. On the other hand, the auxiliary electrode portion 93 protrudes toward the base end side GK in the slit-shaped mixed region MX2 of the mixed region MX.

  A heater 96 made of tungsten is embedded in the auxiliary electrode insulating pipe 95, and two heater terminals 96 a and 96 b of the heater 96 are formed at the base end portion of the auxiliary electrode insulating pipe 95. These heater terminals 96a and 96b are connected to heater connection terminals 170a and 170b extending from the inside of the separator 35 to the front end side GS with respect to the separator 35. Further, these heater connection terminals 170a and 170b are connected to the first heater connection wiring 163a and the second heater connection wiring 163b of the cable 160 described later in the separator 35.

  Next, the outer metal fitting 100 will be described. The outer metal fitting 100 is cylindrical and made of metal, surrounds the inner circumference of the inner metal fitting 20 in a state of being separated from the inner metal fitting 20, and is attached to the exhaust pipe EP having the ground potential PVE to be connected to the ground potential PVE. Is done. The outer metal fitting 100 is composed of a main metal fitting 110, a plug metal fitting 120, and an outer cylinder 130.

  The metal shell 110 is a cylindrical and stainless steel member extending in the axial direction GH. The metal shell 110 is disposed around the radial direction of the pipe holder 40 in the inner metal fitting 20 and separated from the pipe holder 40. The metal shell 110 includes a main body 111, a flange 113, and a metal enclosure 115. Among these, the main body 111 has a cylindrical shape, and has an accommodation hole 111h that penetrates in the axial direction GH. Further, the base end portion of the main body portion 111 is a female screw portion 112 having a female screw formed on the inner periphery thereof. Further, the flange portion 113 has an oval shape protruding outward in the radial direction from the tip of the main body portion 111. The flange portion 113 is formed with two bolt through holes 113h.

  On the other hand, the bracket surrounding portion 115 has a cylindrical shape and protrudes from the flange portion 113 to the distal end side GS. Specifically, the bracket surrounding portion 115 extends to the distal end side GS (the radial inner side CS of the exhaust pipe EP) from the gas contact portion 141 of the first insulating spacer 140, which will be described later, and further to the gas intake of the gas intake pipe 25. It protrudes from the inlet 53h to the tip side GS (radially inner CS). A gas introduction window 115 h is formed in the metal enclosure 115. The gas introduction window 115h is configured such that the entire gas inlet 53h can be visually recognized from the outside of the bracket surrounding portion 115 in the thickness direction DH of the gas intake pipe 25 (the radial direction of the gas intake pipe 25) (FIG. 2). reference). Specifically, the gas introduction window 115h is formed of a U-shaped notch that is open to the front end side GS (upward in FIG. 2) of the metal enclosure portion 115.

  The stopper fitting 120 is a cylindrical and stainless steel member extending in the axial direction GH. The plug fitting 120 has a male screw portion 121 having a male screw formed on the outer periphery thereof, and the male screw portion 121 is screwed into the female screw portion 112 of the metal fitting 110 so that the plug fitting 120 is mainly used. The metal fitting 110 is connected and electrically connected. Further, the plug fitting 120 is arranged around the radial direction of the inner cylinder 30 in the inner fitting 20 and separated from the inner cylinder 30. The plug fitting 120 has a tip pressing portion 123 having a diameter smaller than that of the male screw portion 121 on the tip side GS of the male screw portion 121. On the other hand, it has the hexagonal part 125 which protruded in the flange shape toward the radial direction outer side from the external thread part 121 to the base end side GK, and the outer periphery was made into the hexagonal shape.

  When the male screw part 121 of the plug fitting 120 is screwed into the female screw part 112 of the main metal fitting 110, the plug fitting 120 advances to the distal end side GS, and the distal end pressing portion 123 moves the second insulating spacer 150 described later to the distal end side GS. Press on. Then, this 2nd insulation spacer 150 presses the flange part 45 of the pipe holder 40 toward the front end side GS. Further, the flange portion 45 presses a first insulating spacer 140 described later toward the distal end GS. The first insulating spacer 140 is engaged with the accommodation hole 111 h of the main body 111 of the metal shell 110 via the plate packing 118. As a result, the pipe holder 40, the first insulating spacer 140, the second insulating spacer 150, and the plate packing 118 of the inner metal fitting 20 together with the plug metal fitting 120 are held and integrated with the metal shell 110.

  The outer cylinder 130 is a cylindrical and stainless steel member extending in the axial direction GH. The distal end portion of the outer cylinder 130 is laser welded to the proximal end portion of the plug fitting 120 over the entire circumference, and is electrically connected to the plug fitting 120. The outer cylinder 130 is disposed away from the inner cylinder 30 around the proximal end portion of the inner cylinder 30 in the inner metal fitting 20 and the radial periphery of the distal end portion 160s of the cable 160 described later. Further, the outer end of the base end portion 131 of the outer cylinder 130 has a smaller diameter than the distal end side GS, and is fixed to the cable 160 by caulking. As a result, the base end portion 131 of the outer cylinder 130 passes through the outermost third insulator layer 169 of the cable 160 described later, and is connected to and connected to the ground potential wiring 168 on the inner side. Further, a cylindrical grommet 135 made of insulating rubber is interposed between the outer cylinder 130 and the cable 160.

  Next, the first insulating spacer 140 will be described. The first insulating spacer 140 is a cylindrical member made of alumina that extends in the axial direction GH. The first insulating spacer 140 is interposed between the inner metal fitting 20 and the outer metal fitting 100 to electrically insulate both. Specifically, it is disposed between the front end side portion of the holding part 41 of the pipe holder 40 of the inner metal fitting 20 and the flange part 45 and the metal shell 110 of the outer metal fitting 100.

  The front end portion of the first insulating spacer 140 is exposed in the exhaust pipe EP with the particulate sensor 10 mounted on the exhaust pipe EP (facing the exhaust pipe EP), and the exhaust gas flowing through the exhaust pipe EP. The gas contact portion 141 is in contact with the EG. The gas contact portion 141 has a C-ring inner end surface 141s located at the tip thereof and facing the tip side GS (radial inner side CS of the exhaust pipe EP). As described above, the metal enclosure portion 115 of the metal shell 110 of the outer metal fitting 100 protrudes from the gas contact portion 141 of the first insulating spacer 140 to the tip side GS (radially inner CS). Accordingly, the first insulating spacer 140, including the gas contact portion 141, is entirely surrounded by the metal shell 110 of the outer metal fitting 100 in the axial direction GH (the radial direction CH of the exhaust pipe EP). For this reason, it is difficult for the exhaust gas EG flowing through the exhaust pipe EP to directly hit the gas contact portion 141 of the first insulating spacer 140.

  Next, the second insulating spacer 150 will be described. The second insulating spacer 150 is a cylindrical member made of alumina extending in the axial direction GH. The second insulating spacer 150, together with the first insulating spacer 140, is interposed between the inner metal fitting 20 and the outer metal fitting 100 to electrically insulate both. Specifically, the second insulating spacer 150 is disposed between the proximal end side portion of the holding portion 41 of the pipe holder 40 of the inner metal fitting 20 and the flange portion 45 and the metal shell 110 of the outer metal fitting 100. Has been.

  When attaching the particulate sensor 10 to the exhaust pipe EP, the gas intake pipe 25 of the inner metal fitting 20 is inserted into the exhaust pipe EP from the mounting opening EPO of the mounting portion EPT of the exhaust pipe EP, and adjacent to the mounting opening EPO. The stud bolt EPB provided is inserted into the bolt through hole 113h of the flange portion 113 and fastened with the nut EPN. Thereby, the particulate sensor 10 is fixed to the attachment portion EPT of the exhaust pipe EP, and the outer metal fitting 100 is set to the same ground potential PVE as that of the exhaust pipe EP. An annular gasket holding groove 117 is formed around the accommodation hole 111h in the front end surface 113s of the flange portion 113 of the metal shell 110, and the attachment portion EPT of the exhaust pipe EP and the metal shell 110 are defined as follows. These are bonded in an airtight manner through a copper gasket 119 disposed in the gasket holding groove 117.

  Next, the cable 160 will be described. In the center portion of the cable 160, a second potential wiring 161 made of copper wire, an auxiliary potential wiring 162, a first heater connection wiring 163a and a second heater connection wiring 163b, and a hollow air pipe 164 made of resin are arranged. Yes. And these radial direction circumference | surroundings are coat | covered with the 1st insulator layer 165 which consists of resin. Further, the circumference in the radial direction of the first insulator layer 165 is surrounded by a first potential wiring 166 made of a braided copper wire, and the circumference in the radial direction is covered with a second insulator layer 167 made of resin. ing. Further, the circumference of the second insulator layer 167 is surrounded by a ground potential wiring 168 made of a braided copper thin wire, and the circumference of the second insulator layer 167 is covered with a third insulator layer 169 made of resin. Yes.

  The second potential wiring 161 of the cable 160 is connected to the extending portion 81 of the needle electrode body 80 as described above. Further, the auxiliary potential wiring 162 is connected to the extending portion 91 of the auxiliary electrode body 90. The first heater connection wiring 163a is connected to one heater terminal 96a of the heater 96 through the heater connection terminal 170a, and the second heater connection wiring 163b is connected to the other heater of the heater 96 through the heater connection terminal 170b. It is connected to the terminal 96b. Further, the first potential wiring 166 is caulked and connected to the inner cylinder 30. The ground potential wiring 168 is caulked and connected to the base end portion 131 of the outer cylinder 130. Further, as described above, the front end portion 164s of the air pipe 164 is opened in the inner cylinder 30, so that air (compressed air) AR discharged from the front end portion 164s is passed through the through hole 35h of the separator 35, the pipe holder. It circulates in the discharge space DS through the ventilation through holes 41j of the 40 holding portions 41.

  Next, the circuit unit 200 will be described (see FIG. 1). The circuit unit 200 is connected to the cable 160 of the particle sensor 10 outside the exhaust pipe EP, and has a circuit that drives the particle sensor 10 and detects a signal current Is described later. The circuit unit 200 includes an ion source power supply circuit 210, an auxiliary electrode power supply circuit 240, and a measurement control circuit 220 including a signal current detection circuit 230 and a heater energization circuit 226.

The ion source power supply circuit 210 has a first output terminal 211 having a first potential PV1 and a second output terminal 212 having a second potential PV2. The second potential PV2 is set to a positive high potential with respect to the first potential PV1.
The auxiliary electrode power circuit 240 has an auxiliary first output terminal 241 that is set to the first potential PV1 and an auxiliary second output terminal 242 that is set to the auxiliary electrode potential PV3. The auxiliary electrode potential PV3 is a positive DC high potential with respect to the first potential PV1, but is lower than the peak potential of the second potential PV2.

  The signal current detection circuit 230 in the measurement control circuit 220 has a signal input terminal 231 that is set to the first potential PV1 and a ground input terminal 232 that is set to the ground potential PVE. The signal current detection circuit 230 is a circuit that detects a signal current Is described later. In addition, the heater energization circuit 226 in the measurement control circuit 220 is a circuit that energizes the heater 96 of the auxiliary electrode insulating pipe 95 by PWM control and heats it, and is connected to the first heater connection wiring 163a of the cable 160. The first heater energization end 226a and the second heater energization end 226b connected to the second heater connection wiring 163b of the cable 160 are provided.

In the circuit unit 200, the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 are surrounded by an inner circuit case 250 having a first potential PV1. The inner circuit case 250 houses and surrounds the secondary iron core 271B of the insulating transformer 270 and is electrically connected to the first potential wiring 166 of the cable 160. The insulation transformer 270 has an iron core 271 separated into a primary iron core 271A wound around the primary coil 272 and a secondary iron core 271B wound around the power supply circuit side coil 273 and the auxiliary electrode power supply side coil 274. Configured. Among these, the primary side iron core 271A is conducted to the ground potential PVE, and the secondary side iron core 271B is conducted to the first potential PV1.
Further, the ion source power supply circuit 210, the auxiliary electrode power supply circuit 240, the inner circuit case 250, and the measurement control circuit 220 are surrounded by an outer circuit case 260 having a ground potential PVE. The outer circuit case 260 houses and surrounds the primary iron core 271A of the insulating transformer 270 and is electrically connected to the ground potential wiring 168 of the cable 160.

  The measurement control circuit 220 includes a regulator power source PS. The regulator power supply PS is driven by an external battery BT through the power supply wiring BC. A part of the power input to the measurement control circuit 220 through the regulator power supply PS is distributed to the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 through the isolation transformer 270. The measurement control circuit 220 includes a microprocessor 202 and can communicate with a control unit ECU that controls the internal combustion engine ENG via the communication line CC. The measurement result (signal) of the signal current detection circuit 230 described above A signal such as the magnitude of the current Is) can be transmitted to the control unit ECU.

  The pressure pump 300 is a compressed air source that generates the compressed air AR. Specifically, the pressure feed pump 300 takes in the ambient air (air) around itself, and the air pipe 164 of the cable 160 through the air feed pipe 310 whose tip is inserted into the outer circuit case 260 and the inner circuit case 250. To clean compressed air AR.

Next, the electrical function and operation of the particulate detection system 1 will be described (see FIG. 6). FIG. 6 schematically shows the electrical function and operation of the particle detection system 1 for easy understanding, and there are portions different from the forms described in other drawings.
The acicular electrode body 80 is connected to and connected to the second output terminal 212 of the ion source power supply circuit 210 via the second potential wiring 161 of the cable 160, and is set to the second potential PV2. On the other hand, the auxiliary electrode body 90 is connected to and connected to the auxiliary second output terminal 242 of the auxiliary electrode power circuit 240 via the auxiliary potential wiring 162 of the cable 160, and is set to the auxiliary electrode potential PV3. Furthermore, the inner metal fitting 20 is connected to the inner circuit case 250 and the like via the first electric potential wiring 166 of the cable 160, and is set to the first electric potential PV1. In addition, the outer metal fitting 100 is connected and connected to the outer circuit case 260 and the like via the ground potential wiring 168 of the cable 160, and is set to the ground potential PVE.

Accordingly, the nozzle portion 51 (opposing surface 51t) of the gas intake pipe 25 of the inner metal fitting 20 that is set to the first potential PV1, and the needle-like tip portion 83 that is set to the second potential PV2 that is a positive potential higher than this. In the air, air discharge (corona discharge) occurs. Specifically, a positive needle corona PC in which a corona is generated around the needle-like tip 83 serving as a positive electrode is generated, and N ₂ , O _2, etc. of the atmosphere (air) forming the atmosphere is ionized, and N ³ Positive ions CP such as ⁺ and O ²⁺ are generated. On the other hand, air (compressed air) AR discharged from the tip 164s of the air pipe 164 is supplied into the discharge space DS. For this reason, a part of the generated ions CP is ejected together with the air AR from the nozzle 51n of the nozzle portion 51 to the mixing region MX.

  When the air AR is injected into the cylindrical mixing region MX1 of the mixing region MX, the atmospheric pressure of the cylindrical mixing region MX1 decreases, so that the exhaust gas EG is drawn from the gas inlet 53h through the drawing-in path HK, and the cylindrical mixing region MX1. Incorporated. The intake gas EGI is mixed with the air AR, and is discharged from the gas discharge port 63h via the slit-shaped mixing region MX2 of the mixing region MX and the discharge path EX.

  At this time, if the exhaust gas EG contains fine particles S such as soot, the fine particles S are also taken into the mixing region MX. By the way, the injected air AR contains ions CP. For this reason, the incorporated fine particles S become positively charged charged fine particles SC to which the ions CP adhere, and in this state, together with the air AR from the gas discharge port 63h through the mixing region MX and the discharge path EX. Discharged. On the other hand, among the ions CP ejected to the mixed region MX, the floating ions CPF that have not adhered to the fine particles S receive a repulsive force from the auxiliary electrode portion 93 of the auxiliary electrode body 90 and form the collection electrode 62. Will adhere and will not be discharged.

  Along with the above-described air discharge, the discharge current Id is supplied from the second output end 212 of the ion source power supply circuit 210 to the needle-like tip 83. Most of the discharge current Id flows into the nozzle portion 51 as the power reception current Ij and flows to the first output terminal 211 of the ion source power supply circuit 210. On the other hand, the collection current Ih resulting from the charge of the floating ions CPF collected by the collection electrode 62 also flows to the first output terminal 211 of the ion source power supply circuit 210. That is, a received collection current Ijh (= Ij + Ih) that is the sum of the received current Ij and the collected current Ih flows into the first output terminal 211 of the ion source power supply circuit 210.

However, the power collection current Ijh is smaller than the discharge current Id by a current corresponding to the charge of the discharged ions CPH attached and discharged to the charged fine particles SC. For this reason, the signal current Is corresponding to the difference between the discharge current Id and the received and collected current Ijh (discharge current Id−received and collected current Ijh) flows between the first potential PV1 and the ground potential PVE and balances. Therefore, by detecting the signal current Is corresponding to the charge amount of the discharged ions CPH discharged by the charged fine particles SC, the amount of the fine particles S in the exhaust gas EG can be detected.
In the particulate sensor 10 of the present embodiment, the auxiliary electrode insulating pipe 95 includes the heater 96, so that the auxiliary electrode insulating pipe 95 and the first insulating spacer 140 can be heated. Thereby, the soot adhering to the auxiliary electrode insulating pipe 95 and the first insulating spacer 140 can be removed (evaporated and burned off), and these insulating properties can be recovered or maintained.
As described above, the particulate sensor 10 generates charged charged particulate SC by attaching the ions CP generated by the air discharge to the particulate S contained in the exhaust gas EG taken into the gas intake pipe 25. Then, the amount of fine particles S in the exhaust gas EG is detected using a signal current Is that flows according to the amount of charged fine particles SC between the first potential PV1 and the ground potential PVE.

  As described above, in the particle sensor 10 of the present embodiment, the metal enclosure portion 115 of the outer metal fitting 100 (the main metal fitting 110) is more distal than the gas contact portion 141 of the first insulating spacer 140 (exhaust pipe EP). , Which protrudes radially inward (CS). If the metal enclosure portion 115 of the outer metal fitting 100 has such a configuration, the exhaust gas EG flowing through the exhaust pipe EP does not directly hit the gas contact portion 141 of the first insulating spacer 140, so the exhaust gas is exhausted to the gas contact portion 141. It can suppress that the foreign material (soot, a water droplet, etc.) contained in gas EG adheres. Therefore, in the particulate sensor 10, the first insulating spacer interposed between the inner metal fitting 20 having the gas intake pipe 25 set to the first potential PV1 and the metal fitting surrounding portion 115 of the outer metal fitting 100 set to the ground potential PVE. It can suppress that the insulation of 140 falls, and the quantity of the microparticles | fine-particles S contained in exhaust gas EG can be detected appropriately.

By the way, the amount of the exhaust gas EG taken into the gas intake pipe 25 from the gas inlet 53h is easily affected by the flow velocity of the exhaust gas EG flowing through the exhaust pipe EP. For this reason, detection of the amount of fine particles S contained in the exhaust gas EG is also easily affected by the flow rate of the exhaust gas EG, and it is difficult to improve detection accuracy.
On the other hand, in the fine particle sensor 10 of the present embodiment, the metal enclosure 115 of the outer metal fitting 100 protrudes from the gas inlet 53h of the gas intake pipe 25 to the tip side GS (radially inner CS of the exhaust pipe EP). Yes. When the metal enclosure portion 115 of the outer metal fitting 100 has such a configuration, even when the flow velocity of the exhaust gas EG flowing through the exhaust pipe EP changes greatly, the change in the flow velocity of the exhaust gas EG near the gas inlet 53h. Can be relaxed. For this reason, the change in the amount of the exhaust gas EG taken into the gas intake pipe 25 from the gas inlet 53h is reduced, and the intake amount of the exhaust gas EG is stabilized. Therefore, in this particulate sensor 10, it becomes difficult to be influenced by the flow velocity of the exhaust gas EG flowing through the exhaust pipe EP, and the amount of particulate S contained in the exhaust gas EG can be detected with high accuracy.

  On the other hand, the metal enclosure portion 115 of the outer metal fitting 100 extends from the outside of the metal enclosure portion 115 in the thickness direction DH of the gas intake pipe 25 to at least a part of the gas intake port 53h, in this embodiment, the gas intake port 53h. The gas introduction window 115h has a form in which the entirety can be visually confirmed. For this reason, the exhaust gas EG flowing in the radially outer side of the bracket surrounding portion 115 can be guided directly to the gas inlet 53h through the gas introduction window 115h, so that the exhaust gas EG flowing through the exhaust pipe EP can be used as the gas intake pipe. 25 can be immediately incorporated. Therefore, the amount of fine particles S in the exhaust gas EG can be detected with particularly high responsiveness.

  In particular, in the particulate sensor 10, the signal current Is is very small, but the inner metal fitting 20 having the gas intake pipe 25 set to the first potential PV1 and the metal fitting surrounding portion 115 of the outer metal fitting 100 set to the ground potential PVE. Since the deterioration of the insulating property of the first insulating spacer 140 interposed therebetween is suppressed, the leakage current between the first potential PV1 and the ground potential PVE is suppressed, and the minute signal current Is flowing between them is reduced. The amount can be detected properly. Thus, the amount of fine particles S contained in the exhaust gas EG can be detected appropriately.

(Examples and Comparative Examples)
Subsequently, the result of the test conducted in order to verify the effect of this invention is demonstrated. First, as an example, the fine particle sensor 10 according to the above-described embodiment was prepared (see FIG. 2). In the fine particle sensor 10, as described above, the bracket surrounding portion 115 of the outer metal fitting 100 (the main metal fitting 110) is more distal than the gas contact portion 141 of the first insulating spacer 140 GS (the radially inner CS of the exhaust pipe EP). ) And further to the tip side GS (radially inner CS) from the gas inlet 53h.

  On the other hand, a particulate sensor 901 shown in FIG. 7 was prepared as a comparative example. In this fine particle sensor 901, the metal shell 910 of the outer metal fitting 900 is not provided with a metal enclosure portion, and the outer metal fitting 900 (metal metal fitting 910) is more proximal than the inner end surface 141 s of the gas contact portion 141 of the first insulating spacer 140. It was set as the form located in the side GK (radial direction outer side CK of exhaust pipe EP). Other than that, it was the same as the fine particle sensor 10 of the embodiment.

  Next, the particle sensors 10 and 901 of these examples and comparative examples are respectively attached to the exhaust pipe EP, the flow rate of the exhaust gas EG flowing in the exhaust pipe EP (hereinafter also simply referred to as “flow rate”), the gas intake The inflow amount of exhaust gas EG taken into the gas intake pipe 25 from the inlet 53h (hereinafter also simply referred to as “inflow amount”) and the outflow amount of exhaust gas EG discharged from the gas discharge port 63h (hereinafter simply referred to as “ We investigated the relationship with spill amount ”. The result is shown in FIG. The outflow amount is a value obtained by adding the amount of air (compressed air) AR injected from the nozzle 51n of the nozzle member 50 to the inflow amount.

As can be seen from FIG. 8, in the particulate sensor 901 of the comparative example, the inflow amount and the outflow amount of the exhaust gas EG change greatly under the influence of the flow velocity of the exhaust gas EG. Specifically, it can be seen that as the flow rate of the exhaust gas EG increases, the inflow amount of the exhaust gas EG greatly decreases and the outflow amount of the exhaust gas EG also decreases significantly.
On the other hand, in the fine particle sensor 10 of the embodiment, even if the flow rate of the exhaust gas EG changes, the inflow amount and the outflow amount of the exhaust gas EG hardly change and are not easily affected by the flow rate of the exhaust gas EG. I understand. This is because the flow rate of the exhaust gas EG greatly changes because the bracket surrounding portion 115 of the outer metal fitting 100 protrudes from the gas inlet 53h of the gas intake pipe 25 to the front end side GS (radially inner CS). However, in the vicinity of the gas inlet 53h, the change in the flow rate of the exhaust gas EG can be alleviated. For this reason, it is considered that the inflow amount and the outflow amount of the exhaust gas EG are stabilized.
Thus, compared with the particulate sensor 901 of the comparative example, the particulate sensor 10 of the embodiment is less susceptible to the flow rate of the exhaust gas EG, and therefore the amount of particulate S in the exhaust gas EG can be detected with high accuracy.

(Modification 1)
Next, the particle sensor 401 according to the first modification will be described (see FIG. 9). In the particle sensor 401, the outer metal fitting 400 is different from the outer metal fitting 100 of the particle sensor 10 according to the embodiment. Specifically, in the first modification, in the outer metal fitting 400, the dimension in the axial direction GH (the radial direction CH of the exhaust pipe EP) of the metal fitting enclosure 415 of the main metal fitting 410 is larger than that of the metal fitting enclosure 115 of the embodiment. The bracket surrounding portion 415 is located closer to the base end side GK (radially outer side CK) than the gas intake port 53h.

  However, the metal enclosure portion 415 of the outer metal fitting 400 also protrudes from the gas contact portion 141 of the first insulating spacer 140 to the tip side GS (radially inner CS). For this reason, it can suppress that the foreign material in exhaust gas EG adheres to the gas contact part 141 of the 1st insulating spacer 140. FIG. Therefore, the particulate sensor 401 can also suppress the deterioration of the insulating property of the first insulating spacer 140, and can appropriately detect the amount of the particulate S contained in the exhaust gas EG.

(Modification 2)
Next, the particle sensor 501 according to the second modification will be described (see FIG. 10). In this particle sensor 501, the form of the outer metal fitting 500 is different from the outer metal fitting 100 of the particle sensor 10 according to the embodiment. Specifically, in the second modification, in the outer metal fitting 500, the dimension in the axial direction GH (the radial direction CH of the exhaust pipe EP) of the metal fitting enclosure 515 of the metal shell 510 is larger than that of the metal fitting enclosure 115 of the embodiment. Further, the bracket surrounding portion 515 protrudes from the gas discharge port 63h to the tip side GS (radially inner CS).

  However, similarly to the particle sensor 10 according to the embodiment, the gas introduction window 515h formed of a U-shaped notch in a plan view provided in the metal fitting enclosure 515 has a metal enclosure enclosure in the thickness direction DH of the gas intake pipe 25. From the outside of 515, the entire gas inlet 53h is visible. In addition, the gas introduction window 515h is configured such that the entire gas discharge port 63h can be visually recognized from the outside of the metal enclosure 515 in the thickness direction DH of the gas intake pipe 25.

Since the metal enclosure portion 515 of the outer metal fitting 500 also protrudes to the tip side GS (radially inner CS) from the gas contact portion 141 of the first insulating spacer 140, the exhaust gas is exhausted to the gas contact portion 141 of the first insulating spacer 140. It can suppress that the foreign material in gas EG adheres. Therefore, the particulate sensor 501 can also suppress the deterioration of the insulating property of the first insulating spacer 140, and can appropriately detect the amount of particulate S contained in the exhaust gas EG.
Further, similarly to the particulate sensor 10 according to the embodiment, the metal enclosure portion 515 of the outer metal fitting 500 protrudes from the gas intake port 53h of the gas intake pipe 25 to the tip side GS (radially inner CS of the exhaust pipe EP). Yes. Therefore, the particulate sensor 501 is also less susceptible to the flow rate of the exhaust gas EG flowing through the exhaust pipe EP, and can detect the amount of particulate S contained in the exhaust gas EG with high accuracy. Similarly to the particulate sensor 10 according to the embodiment, the gas introduction window 115h is configured such that the entire gas inlet 53h can be visually recognized from the outside of the metal enclosure 515 in the thickness direction DH of the gas intake pipe 25. . For this reason, the particulate sensor 501 can also detect the amount of particulate S in the exhaust gas EG with particularly high responsiveness.

In the above, the present invention has been described with reference to the embodiment and the first and second modifications. However, the present invention is not limited to the above-described embodiment and the first and second modifications, and is within a scope not departing from the gist thereof. Needless to say, the invention can be applied with appropriate changes.
For example, in the embodiment and the like, the gas introduction windows 115h and 515h are notched in a U shape in plan view, but are not limited thereto. For example, instead of the gas introduction windows 115h and 515h, the gas introduction window may be a through hole such as a circle, an ellipse, or a rectangle.

  In the embodiment and the second modification, the gas introduction windows 115h and 515h are configured such that the entire gas inlet 53h can be visually recognized from the outside of the metal enclosures 115 and 515 in the thickness direction DH of the gas intake pipe 25. Not limited to this. The gas introduction window may be configured such that only a part of the gas inlet 53h can be visually recognized from the outside of the metal enclosures 115 and 515 in the thickness direction DH of the gas intake pipe 25. Even in this case, the exhaust gas EG flowing outside the metal enclosures 115 and 515 in the radial direction can be directly led to the gas inlet 53h through the gas introduction window, so that the exhaust gas EG is immediately taken into the gas intake pipe 25. be able to.

In the embodiment and the like, in order to detect the fine particles S, ions CP are generated in the discharge space DS, and the ions CP are mixed with the fine particles S in the mixing region MX. However, the configuration of the particle sensor is not limited to this. The ions CP may be generated in the mixing region MX and mixed with the fine particles S. For example, a configuration may be adopted in which a discharge electrode body having the second potential PV2 is disposed in the mixed region MX and corona discharge is generated between the inner metal fitting 20 and the discharge electrode body.
Further, in the embodiment and the like, the compressed air AR is injected into the mixing region MX using the pressure pump 300. However, a configuration may be adopted in which only the exhaust gas (measured gas) EG is supplied to the mixing region MX without using the pressure feed pump 300 and the compressed air AR.

DESCRIPTION OF SYMBOLS 1 Particulate detection system 10,401,501 Particulate sensor 20 Inner metal fitting 25 Gas intake pipe 50 Nozzle member 53h Gas inlet 60 Mixing discharge member 63h Gas outlet 100,400,500 Outer metal fitting 110,410,510 Main metal fitting 115,415 , 515 Metal enclosures 115h, 515h Gas introduction window 140 First insulating spacer 141 Gas contact portion 141s Inner end face CH (exhaust pipe) radial CS radial inner CK radial outer DH (gas intake pipe) thickness direction EP Exhaust Pipe (venting pipe)
EG Exhaust gas (measured gas)
EGI Intake gas S Fine particles SC Charged fine particles CP Ion PVE Ground potential PV1 First potential Is Signal current

Claims (4)

A gas to be measured containing fine particles circulates and is attached to a metal vent pipe that is at ground potential.
A fine particle sensor comprising an inner metal fitting having a gas intake pipe including a gas intake port for taking a gas to be measured into the first potential different from the ground potential,
A cylindrical outer metal fitting having a cylindrical metal enclosure surrounding the radial circumference of the inner metal fitting, which is attached to the vent pipe to be the ground potential;
A tubular shape having a gas contact portion in contact with the gas to be measured which is interposed between the inner metal fitting and the metal fitting enclosure portion of the outer metal fitting and electrically insulated from each other and circulates in the ventilation pipe. And an insulating spacer.
The bracket enclosure of the outer bracket is
A fine particle sensor having a form protruding from the gas contact portion of the insulating spacer to the radially inner side of the vent pipe. The fine particle sensor according to claim 1,
The bracket surrounding portion of the outer bracket is
Projecting radially inward from the gas inlet of the gas intake pipe, and
A fine particle sensor having a gas introduction window in a form in which at least a part of the gas inlet can be visually recognized from the outside of the bracket surrounding portion in the thickness direction of the gas intake pipe. The fine particle sensor according to claim 2,
The gas introduction window of the metal enclosure portion is
The fine particle sensor which has a form which can visually recognize the whole of the above-mentioned gas intake from the outside of the above-mentioned metal enclosure part in the thickness direction of the above-mentioned gas intake pipe. The fine particle sensor according to any one of claims 1 to 3,
Charged fine particles are generated by attaching ions generated by air discharge to the fine particles contained in the gas to be measured taken into the gas intake tube, and the first potential and the ground potential are generated. A fine particle sensor that detects the amount of fine particles in the gas to be measured using a signal current that flows in accordance with the amount of the charged fine particles.

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