JP2017020802A - Fine particle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine particle sensor that is resistant to occurrence of a discharge and current leakage between a discharge potential terminal member and a cylindrical body through a surface of a first insulating member even when an insulation property of the surface of the first insulating member falls.SOLUTION: A first insulating member 71 is configured to include: an alternative route SD1 on a tip end side via a first via point P1 where the shortest creepage route SCR on the tip end side from a tip most-end contact part 71n on an inner side to a tip most-end contact part 71w on an outer side is located on a side opposite a side where the tip most-end contact part 71w on the outer side is located as to an axial line direction GH when viewed from the tip most-end contact part 71n on the inner side of a creepage route CR from a contact part 71h on the inner side to a contact part 71v on the outer side through a surface of the first insulating member; and an alternative route KD1 on a base end side via a third via point P3 where the shortest creepage route KCR on the base end side from a base most-end contact part 71y on the inner side to a base most-end contact part 71x on the outer side is located on a side opposite a side where the base most-end contact part 71x on the outer side is located as to the axial line direction GH when viewed from the base most-end contact part 71y on the inner side.SELECTED DRAWING: Figure 9

Description

  The present invention relates to a fine particle sensor that detects fine particles in a gas to be measured.

  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 directly detecting the amount of particulates in exhaust gas and detecting the amount of particulates in exhaust gas in order to detect a filter failure.

  As such a fine particle sensor, for example, as disclosed in Patent Document 1, an air discharge (corona discharge) is generated between a first member having a first reference potential and the first member. A discharge electrode body is known. In this fine particle sensor, a discharge potential higher than the first reference potential in a state where the fine particle sensor is attached to a vent pipe (for example, an exhaust pipe) through which a gas to be measured (for example, exhaust gas) containing fine particles flows. Is applied to the discharge electrode body to generate an air discharge (corona discharge) between the discharge electrode body and the first member. As a result, ions are generated around the discharge electrode body, and fine particles in the gas to be measured are detected using the ions.

JP 2014-10099 A

  By the way, the inventor of the present application is examining a fine particle sensor 510 having a structure as shown in FIG. 11 (for example, see Japanese Patent Application No. 2014-103518). The fine particle sensor 510 is attached to the exhaust pipe EP of the engine and detects fine particles S such as soot in the exhaust gas EG (measured gas) flowing through the exhaust pipe EP. The fine particle sensor 510 includes an inner protector 445 (first member) that is set to a first reference potential, and a ceramic element 400 (sensor element), and a base end side in the axial direction GH (vertical direction in FIG. 11) (FIG. 11). In FIG. 11, it extends from the upper side to the tip side (lower side in FIG. 11). The ceramic element 400 includes a ceramic base 401 (insulating base) made of an electrical insulating material and extending in the axial direction GH, and a discharge electrode body 410 provided on the ceramic base 401, which has a higher potential than the first reference potential. Is applied to the inner protector 445 to generate an air discharge (corona discharge) between the inner protector 445 and the discharge electrode body 410 and is formed on the surface of the ceramic substrate 401. It has a discharge potential pad 413 to be a potential (see FIG. 12).

  Further, the particle sensor 510 is connected to the discharge potential lead wire 461 and is made of a discharge potential terminal member 473 that is set to a discharge potential, and is made of metal and has a cylindrical shape extending in the axial direction GH, and is electrically connected to the inner protector 445. An inner cylinder 480 (cylindrical body) having one reference potential and a first insulating member 471 made of an electrical insulating material, extending in the axial direction GH, and positioned inside the inner cylinder 480 (see FIG. 11). The first insulating member 471 accommodates the discharge pad portion 400P where the discharge potential pad 413 is located and the discharge potential terminal member 473 in the ceramic element 400 in the first insulating member 471, and the discharge potential terminal member 473 is discharged into the discharge potential. While holding the discharge potential terminal member 473 in contact with the pad 413, the discharge potential terminal member 473 and the inner cylinder 480 are electrically insulated.

  By the way, the outer side surface 471b of the first insulating member 471 is in contact with the inner peripheral surface 480c of the inner cylinder 480 (see FIG. 11). Therefore, when the surface of the first insulating member 471 is deteriorated due to water droplets adhering to the surface of the first insulating member 471 or the first insulating member 471 having a high temperature, the first insulating member There is a possibility that discharge (spark discharge) or current leakage may occur between the discharge potential terminal member 473 (discharge potential) and the inner cylinder 480 (first reference potential) through the surface of the member 471.

  Specifically, the inner side surface 471 f of the first insulating member 471 has an inner contact portion 471 h that contacts the discharge potential terminal member 473. The inner contact portion 471h includes an innermost frontmost contact portion 471n located on the most distal side GS in the axial direction GH (see FIG. 13). In addition, the outer surface 471 b of the first insulating member 471 has an outer contact portion 471 v that contacts the inner peripheral surface 480 c of the inner cylinder 480. The outer contact portion 471v has an outermost distal contact portion 471w located on the most distal side GS in the axial direction GH. Therefore, for example, as shown in FIG. 13, in the creeping path CR from the inner contact portion 471 h to the outer contact portion 471 v through the surface of the first insulating member 471, the inner most distal contact portion 471 n to the outer most distal contact portion 471 w. There is a possibility that spark discharge may occur between the discharge potential terminal member 473 and the inner cylinder 480 in the shortest creepage path SCR leading to the front end. When such discharge (spark discharge) or current leak occurs, there is a possibility that fine particles in the gas to be measured cannot be detected properly.

  The present invention has been made in view of such a problem, and even when the insulating property of the surface of the first insulating member is lowered, the cylinder made of the discharge potential terminal member and the metal through the surface of the first insulating member. It is an object of the present invention to provide a fine particle sensor in which discharge and current leakage are unlikely to occur with a state body.

  One aspect of the present invention is a first member having a first reference potential, an insulating base made of an electrical insulating material and extending in the axial direction, and a discharge electrode body provided on the insulating base, A discharge potential higher than one reference potential and causing an air discharge between the first member and the discharge electrode body, and the discharge electrode body is electrically connected to the surface of the insulating substrate; And a sensor element having a discharge potential pad formed as the discharge potential, and having a configuration extending from the base end side to the tip end side in the axial direction, and being connected to the discharge potential lead wire. A discharge potential terminal member to be the discharge potential; a cylindrical body made of metal and extending in the axial direction; electrically connected to the first member to be the first reference potential; and electrical insulation Made of material and has a cylindrical shape that extends in the axial direction A first insulating member located inside the cylindrical body, wherein the discharge pad portion of the sensor element where the discharge potential pad is located and the discharge potential terminal member are housed inside the first insulating member; Holding the discharge potential terminal member while bringing the discharge potential terminal member into contact with the discharge potential pad, and electrically insulating between the discharge potential terminal member and the cylindrical body, And the inner surface of the first insulating member has an inner contact portion that contacts the discharge potential terminal member, and the inner contact portion is located on the most distal side in the axial direction among the inner contact portions. An innermost distal end contact portion and an innermost proximal end contact portion located closest to the proximal end side in the axial direction, and an outer surface of the first insulating member is an inner peripheral surface of the cylindrical body. Has an outer contact portion to contact and The outer contact portion includes an outer most distal contact portion positioned closest to the distal end in the axial direction and an outermost proximal contact portion positioned closest to the proximal end in the axial direction. And the first insulating member has a tip extending from the inner most distal contact portion to the outer most distal contact portion in a creeping path from the inner contact portion to the outer contact portion through the surface of the first insulating member. A side shortest creepage path is a first via point located on the opposite side to the side on which the outer most distal contact portion is located in the axial direction when viewed from the inner most distal contact portion, or the outer most distal contact portion. As viewed from the front end side detour route passing through the second via point located on the opposite side to the side where the inner most advanced contact portion is located in the axial direction, and the inner side of the creeping route Above the most proximal contact The proximal-side shortest creepage path leading to the outermost proximal end contact portion is located on the side opposite to the side where the outermost proximal end contact portion is located in the axial direction when viewed from the innermost proximal contact portion. A proximal end passing through a third waypoint or a fourth waypoint located on the side opposite to the side where the innermost proximal contact portion is located in the axial direction as viewed from the outermost proximal contact portion. It is a fine particle sensor having a form including a side detour path.

In the fine particle sensor described above, the first insulating member has the following form. Specifically, the first insulating member passes through the surface of the first insulating member from the inner contact portion (the portion of the inner surface of the first insulating member that contacts the discharge potential terminal member) to the outer contact portion (of the first insulating member). Out of the creeping path leading to the inner peripheral surface of the cylindrical body of the outer surface, the innermost contact portion (the portion of the inner contact portion located closest to the tip in the axial direction) is the outermost contact point. The tip side shortest creepage path leading to the portion (the portion of the outer contact portion that is located closest to the tip side in the axial direction) is “the outermost tip contact portion is located in the axial direction as viewed from the inner tip contact portion. The first via point located on the opposite side to the side (ie, the side away from the outer cutting edge contact portion in the axial direction), or “the inner cutting edge contact portion in the axial direction as viewed from the outer cutting edge contact portion” Opposite side That is, there is a form that includes a distal end side detour path passing through the second via-points "located on the side) away about axially from the inner cutting edge contact.
As described above, the first insulating member is configured such that the tip-side shortest creepage path includes the above-described detour path (tip-side detour path), so that the tip-side shortest creepage path includes the detour path. Compared with the case where there is no configuration, it is possible to lengthen the tip side shortest creepage route by the length of the tip side detour route.

Further, in the fine particle sensor described above, the first insulating member has the following form. Specifically, the first insulating member is formed from the innermost proximal end contact portion (the portion of the inner contact portion located closest to the proximal end side in the axial direction) to the outermost proximal end contact portion (the axial direction of the outer contact portion). The shortest creepage path on the base end side that reaches the most proximal end portion is “on the side opposite to the side on which the outermost proximal contact portion is positioned in the axial direction as viewed from the innermost proximal contact portion (that is, , A third via point located on the side away from the outermost proximal contact portion in the axial direction), or “the innermost proximal contact portion in the axial direction as viewed from the outermost proximal contact portion. It is configured to include a proximal-side detour path that passes through a “fourth waypoint located on the opposite side to the side (that is, the side away from the innermost proximal-end contact portion in the axial direction)”.
As described above, the first insulating member is configured such that the shortest creepage path on the base end side includes the detour path as described above (the detour path on the base end side), so that the detour path on the shortest creepage path on the base end side. Compared to the case where the shape is not included, the shortest creepage path on the base end side can be lengthened by the length of the detour path on the base end side.

  Therefore, in the above-described fine particle sensor, even if water droplets adhere to the surface of the first insulating member or the temperature of the first insulating member becomes high, the first insulating member has a reduced insulating property on the surface of the first insulating member. Discharge and current leakage between the discharge potential terminal member and the cylindrical body through the surface of the insulating member are less likely to occur.

  Examples of the sensor element in which the discharge electrode body is provided on the insulating base include a ceramic base made of an insulating ceramic such as alumina and a part of the discharge electrode body included. In addition, for example, after forming a discharge electrode body on the surface of a ceramic substrate, a discharge electrode body is provided on an insulating substrate made of a ceramic substrate and a glass coat by partially coating the discharge electrode body with a glass coat. Also included are sensor elements.

  Further, in the fine particle sensor, the sensor element has a different potential pad formed on a surface of the insulating base and having a different potential different from the discharge potential, and the fine particle sensor has a different potential. A second electric potential terminal member connected to a lead wire and made of the different electric potential, and made of an electrically insulating material, has a cylindrical shape extending in the axial direction, and is adjacent to the first insulating member in the axial direction. A different potential pad portion where the different potential pad is located in the sensor element and the different potential terminal member are housed in the second insulating member, and the different potential terminal member is accommodated in the different potential pad. A second insulating member that holds the different potential terminal member in contact with the cylindrical member, and the cylindrical body is in contact with the second insulating member, and the second insulating member and the first insulating member in the axial direction. Fix the member May the fine particle sensor having a fixed portion.

  As described above, the fine particle sensor has an outer contact portion in which the outer surface of the first insulating member is in contact with the inner peripheral surface of the cylindrical body. In this way, the first insulating member is brought into the radial direction by bringing the outer surface (outer peripheral surface) of the first insulating member into contact with the inner peripheral surface of the cylindrical body located on the radially outer side of the first insulating member. Can be fixed.

  Further, the fine particle sensor described above is made of an electrical insulating material, has a cylindrical shape extending in the axial direction, and includes a second insulating member adjacent to the first insulating member in the axial direction. The second insulating member accommodates the different potential pad portion and the different potential terminal member of the sensor element in the second insulating member, and holds the different potential terminal member while bringing the different potential terminal member into contact with the different potential pad. It is an insulating member. Furthermore, in the above-described fine particle sensor, the cylindrical body has a fixing portion that contacts the second insulating member and fixes the second insulating member and the first insulating member in the axial direction. Therefore, in the fine particle sensor described above, the first insulating member can be fixed to the cylindrical body not only in the radial direction but also in the axial direction.

It is the schematic of the vehicle carrying the particulate sensor concerning embodiment. It is a longitudinal cross-sectional view of the fine particle sensor concerning embodiment. It is a disassembled perspective view of the particulate sensor. It is a schematic diagram of a particulate detection system. It is a perspective view of the ceramic element which comprises a fine particle sensor. It is a disassembled perspective view of the ceramic element. It is explanatory drawing of the microparticle detection system concerning embodiment. It is a part of longitudinal section of the particulate sensor concerning an embodiment. It is the C section enlarged view of FIG. It is an enlarged view of the particulate sensor concerning a modification. It is a longitudinal cross-sectional view of the particulate sensor concerning a reference form. It is a perspective view of the ceramic element which comprises the fine particle sensor. It is the D section enlarged view of FIG.

(Embodiment)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a vehicle AM equipped with a particulate detection system 1 according to the embodiment. FIG. 2 is a cross-sectional view of the particle sensor 10 according to the present embodiment. FIG. 3 is an exploded perspective view of the particle sensor 10. FIG. 4 is a schematic diagram of the particulate detection system 1. However, in FIG. 4, 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. In FIG. 2, the side (downward in FIG. 2) on which the inner protector 45 is disposed in the axial direction GH of the particulate sensor 10 (the direction in which the axis AX extends, the vertical direction in FIG. 2) is the tip side GS, The side (upward in FIG. 2) from which the opposite electric wires 165, 166 and the like extend is defined as a base end side GK.

  The particulate detection system 1 (hereinafter also simply referred to as the system 1) includes a particulate sensor 10 and a control device 200 as shown in FIG. This system 1 is mounted on an exhaust pipe EP of an engine ENG mounted on a vehicle AM, and detects fine particles S such as soot in an exhaust gas EG (measured gas) flowing through the exhaust pipe EP. Specifically, the particulate sensor 10 is fixed to the 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 to 168, and has a circuit that drives the particle sensor 10 and detects a signal current Is described later (see FIGS. 1 and 4). ). Among the electric wires 165 to 168, the electric wires 165 and 166 are triple coaxial cables (triaxial cables), 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), and the electric wire 166 includes an auxiliary potential lead wire 162 as a core wire (center conductor) (see FIGS. 3 and 4). 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. 3 and 4).

  Next, the control device 200 will be described with reference to FIG. The control device 200 includes a measurement control circuit 220 including a signal current detection circuit 230 and a heater energization circuit 226, an ion source power supply circuit 210, and an auxiliary electrode power supply circuit 240.

  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).

  On the other hand, the auxiliary electrode power circuit 240 has an auxiliary first output terminal 241 that is set to the sensor GND potential SGND, and an auxiliary second output terminal 242 that is set to the auxiliary potential PV3 (different potential different from the discharge potential PV2). ing. The auxiliary second output terminal 242 is connected to the auxiliary potential lead wire 162. The auxiliary potential PV3 is a positive DC high potential with reference to the sensor GND potential SGND. However, the auxiliary potential PV3 is lower than the peak potential of the discharge potential PV2 (for example, a potential of DC 100 to 200 V).

  Further, in the measurement control circuit 220, the signal current detection circuit 230 has a signal input terminal 231 and a ground input terminal 232. Among these, the signal input terminal 231 is connected to the first output terminal 211 of the ion source power supply circuit 210 that is set to the sensor GND potential SGND. On the other hand, the ground input terminal 232 is connected to the chassis GND potential CGND. Chassis GND potential CGND and sensor GND potential SGND are electrically insulated from each other. With such a configuration, the signal current detection circuit 230 detects the signal current Is flowing between the signal input terminal 231 (sensor GND potential SGND) and the ground input terminal 232 (chassis GND potential CGND).

  The heater energization circuit 226 is a circuit that energizes a heater portion 130 of the ceramic 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. 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. In addition, the first heater energization end 226a and the first heater lead wire 163 are set to potentials based on the chassis GND potential CGND.

  Further, the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 are 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 circuit 210, the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240, and the signal input terminal 231 of the signal current detection circuit 230 are connected to the inner circuit case 250.

  In the present embodiment, the inner circuit case 250 encloses and surrounds the ion source power circuit 210, the auxiliary electrode power circuit 240, and the secondary iron core 271B of the insulating transformer 270. The sensor GND potential SGND is established by conducting to the first output terminal 211 and the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240. The first output terminal 211 of the ion source power circuit 210 and the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240 are connected to the sensor GND potential SGND of the coaxial double outer conductors 165G and 166G of the electric wires 165 and 166, respectively. Are connected to the inner outer conductors 165G1 and 166G1.

  The insulation transformer 270 is separated into a primary side core 271A in which the iron core 271 is wound around the primary side coil 272 and a secondary side iron core 271B in which the power supply circuit side coil 273 and the auxiliary electrode power source side coil 274 are wound. Configured. 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 auxiliary electrode power supply circuit 240, the inner circuit case 250, and the measurement control circuit 220 including the signal current detection circuit 230 and the heater energization circuit 226 have an outer circuit case having a chassis GND potential CGND. 260. Further, the ground input terminal 232 of the signal current detection circuit 230, the second heater power supply terminal 226b of the heater power supply circuit 226, and the primary side iron core 271A of the insulation transformer 270 are connected to the outer circuit case 260 to be connected to the chassis GND potential. CGND.

  In the present embodiment, the outer circuit case 260 includes therein an ion source power supply circuit 210, an auxiliary electrode power supply circuit 240, an inner circuit case 250, a signal current detection circuit 230, and a heater energization circuit 226. 220 and the primary side iron core 271A of the insulating transformer 270 are accommodated and enclosed. Further, the outer circuit case 260 is electrically connected to the outer outer conductors 165G2 and 166G2 of the coaxial double outer conductors 165G and 166G of the electric wires 165 and 166, which are set to the chassis GND potential CGND.

  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. As a result, the measurement result (the magnitude of the signal current Is) of the signal current detection circuit 230 described above or a value obtained by converting the measurement result into the amount of fine particles 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 and the auxiliary electrode power supply circuit 240 through the insulating transformer 270. The insulating transformer 270 forms 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 a part of the auxiliary electrode power circuit 240. The auxiliary electrode power supply side coil 274 and the iron core 271 (primary side iron core 271A, secondary side iron core 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 and the auxiliary electrode power supply circuit 240, electrical insulation between them can be maintained.

Next, the particle sensor 10 will be described with reference to FIGS.
As shown in FIG. 2, the particle sensor 10 has a configuration extending from the base end side (upper side in FIG. 2) to the front end side (lower side in FIG. 2) in the axial direction GH (vertical direction in FIG. 2). The fine particle sensor 10 has a plate shape extending in the axial direction GH, and includes a ceramic element 100 (sensor element) that generates ions by air discharge. In addition, a metal shell 50 is provided which holds the ceramic element 100 while ensuring electrical insulation from the ceramic element 100 and is used as 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 male screw for fixing the particulate sensor 10 to the exhaust pipe EP on the outer periphery of the distal end portion 90 s on the distal end side GS from the flange portion 91. Accordingly, the particulate sensor 10 is attached to a metal mounting boss BO that is separately fixed to the exhaust pipe EP using a male screw at the tip end 90s of the mounting bracket 90, and the exhaust gas is exhausted through the mounting boss BO. Fixed to the tube EP. 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 proximal end side GK of the mounting bracket 90. Specifically, the distal end portion 95s of the outer cylinder 95 is fitted on the proximal end portion 90k of the mounting bracket 90, and the proximal end portion 90k of the mounting bracket 90 and the distal end portion 95s of the outer barrel 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 arranged via a first insulating spacer 60 and a second insulating spacer 61 made of an electrical insulating material. Yes. 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. Further, the inner cylinder 80 is made of metal and has a cylindrical shape extending in the axial direction GH, and a tip portion thereof is an annular flange portion 81. Then, the distal end portion 80 s of the inner cylinder 80 is externally fitted to the proximal end portion 50 k of the metallic shell 50 so that the flange portion 81 of the inner metallic shell 50 contacts the flange portion 51 of the metallic shell 50, and The metal shell 50 and the inner cylinder 80 are integrated with each other by laser welding the end 50k and the tip 80s of the inner cylinder 80.

  Further, the metal shell 50 and the inner cylinder 80 that are integrated with each other are provided with a first insulating spacer 60 that is positioned on the distal end GS and a second insulating spacer 61 that is positioned on the proximal end GK. It is sandwiched and arranged in the mounting bracket 90. Further, a sleeve 62 is disposed on the proximal end side GK of the second insulating spacer 61. A wire packing 63 is disposed between the most proximal end portion 90kk of the mounting bracket 90 and the sleeve 62, and the most proximal 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 ceramic element 100 is inserted into the hole 52b. Further, around the ceramic element 100, a cylindrical ceramic holder 53 made of alumina and holding the ceramic element 100 in order from the front end side GS to the base end side GK, 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 most proximal end portion 50 kk of the metal shell 50 and the ceramic sleeve 56. The most proximal end portion 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 ceramic element 100 is also held airtight by the metal shell 50.

  Further, an inner protector 45 and an outer protector 40, which are made of stainless steel and have a double cylindrical shape, are fixedly provided at the distal end portion 50s of the metal shell 50 so as to surround the distal end portion of the ceramic element 100 from the radially outer side. Yes. The inner protector 45 and the outer protector 40 protect the ceramic element 100 from water droplets and foreign matters, and guide the exhaust gas EG to the periphery of the ceramic element 100. The inner protector 45 and the outer protector 40 are fixed to the tip 50s of the metal shell 50 as follows. Specifically, the large diameter portion 47 of the proximal end side GK of the inner protector 45 is fitted on the distal end portion 50s of the metal shell 50, and further, the large diameter portion of the proximal end side GK of the outer protector 40 is disposed on the outer side. After the outer fitting of 42, these fitting portions are fixed by laser welding.

  In the outer protector 40, the cylindrical body portion 41 is formed with a plurality of rectangular outer introduction holes 40I on the periphery of the tip side GS for introducing the exhaust gas EG therein. Further, the cylindrical body portion 46 of the inner protector 45 is formed with a plurality of triangular and round inner introduction holes 45I on the periphery of the distal end side GS and the proximal end side GK, respectively (FIGS. 2 and 3). Further, a round discharge port 45O for discharging the introduced exhaust gas EG (gas to be measured) is formed at the tip portion of the inner protector 45, and the tip portion of the inner protector 45 including the discharge port 45O is formed. Projecting outward from the opening 43 at the tip of the outer protector 40.

  Here, with reference to FIG. 7, intake and exhaust of the exhaust gas EG to the inner protector 45 and the outer protector 40 when the particulate sensor 10 is used will be described. In FIG. 7, 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 outer protector 40 and the inner protector 45 of the particulate sensor 10, the flow velocity rises outside the discharge port 45O of the inner protector 45, and due to the venturi effect. A negative pressure is generated in the vicinity of the discharge port 45O.

  Then, due to this negative pressure, the intake exhaust gas EGI taken into the inner protector 45 is exhausted from the exhaust port 45O. At the same time, the exhaust gas EG around the outer introduction hole 40I of the outer protector 40 is taken into the outer protector 40 from the outer introduction hole 40I, and further into the inner protector 45 through the inner introduction hole 45I of the inner protector 45. Incorporated. And since the intake exhaust gas EGI in the inner protector 45 is discharged from the discharge port 45O, in the inner protector 45, the inner introduction hole 45I on the base end side GK is directed toward the discharge port 45O on the front end side GS. An air flow of flowing intake exhaust gas EGI is generated.

  Further, in the fine particle sensor 10 of the present embodiment, as shown in FIG. 2, at the proximal end side GK of the metal shell 50 (specifically, the proximal end side GK of the ceramic sleeve 56), An insulating holder 70 made of an electrical insulating material is disposed. The insulating holder 70 is formed with an insertion hole 70c penetrating the insulating holder 70 in the axial direction GH (see FIG. 3), and the ceramic element 100 is inserted into the insertion hole 70c.

  A first insulating member 71 is disposed adjacent to the insulating holder 70 on the proximal end side GK of the insulating holder 70. 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 adjacent to the first insulating member 71 on the proximal 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. The first insulating member 71 and the second insulating member 72 are disposed adjacent to each other in the axial direction GH, and both are accommodated inside the inner cylinder 80.

  The first insulating member 71 has an insertion hole 71c that penetrates itself in the axial direction GH. The ceramic element 100 is inserted into the insertion hole 71c, and the discharge pad portion 100P (see FIG. 5) where the discharge potential pad 113 is located in the ceramic element 100 and the discharge potential terminal member 73 are accommodated. Yes.

  On the other hand, the second insulating member 72 has a first insertion hole 72c and a second insertion hole 72d penetrating itself in the axial direction GH. In the second insertion hole 72d, a different potential in which an auxiliary potential pad 125 (different potential pad) that is different from the discharge potential PV2 (specifically, the auxiliary potential PV3) of the ceramic element 100 is located. The potential pad portion 100R (see FIG. 5) is accommodated. The second insulating member 72 accommodates an auxiliary potential terminal member 75, a first heater terminal member 76, and a second heater terminal member 77, which will be described later, in the second insertion hole 72d in a state of being insulated from each other. 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. 5) of the ceramic element 100 in the insertion hole 71c. Yes. Specifically, the discharge potential terminal member 73 is held in a manner sandwiched between the discharge potential pad 113 of the ceramic element 100 and the inner surface 71f constituting the insertion hole 71c of the first insulating member 71 in the insertion hole 71c. (See FIGS. 8 and 9). As a result, the discharge potential terminal member 73 is brought into contact with the discharge potential pad 113 of the ceramic element 100 in the insertion hole 71c. At the same time, the first insulating member 71 electrically insulates the discharge potential terminal member 73 from the inner cylinder 80.

Further, the inner side surface 71f of the first insulating member 71 has an inner contact portion 71h that contacts the discharge potential terminal member 73 (see FIG. 9). As shown in FIG. 9, the inner contact portion 71h is the innermost tip contact located on the most distal side GS (lower side in FIG. 9) in the axial direction GH (vertical direction in FIG. 9) of the inner contact portion 71h. 71n and the innermost proximal contact portion 71y located on the most proximal side GK (upper side in FIG. 9) in the axial direction GH.
Moreover, the outer side surface 71b of the 1st insulating member 71 has the outer side contact part 71v which contacts the inner peripheral surface 80c of the inner cylinder 80 (refer FIG. 9). This outer contact portion 71v has a cylindrical shape, and the outermost contact portion 71w located on the most distal side GS in the axial direction GH of the outer contact portion 71v and the most proximal side GK in the axial direction GH. And the outermost proximal end contact portion 71x.

  As described above, in the particle sensor 10 of the present embodiment, the outer surface 71b of the first insulating member 71 has the cylindrical outer contact portion 71v that contacts the inner peripheral surface 80c of the inner tube 80 (FIG. 3, see FIG. In this way, the first insulating member 71 is brought into contact with the inner peripheral surface 80c of the inner cylinder 80 positioned on the outer side in the radial direction of the first insulating member 71 by bringing the outer surface 71b (outer peripheral surface) of the first insulating member 71 into contact therewith. 71 can be fixed in the radial direction (positional displacement in the radial direction can be prevented).

  In addition, the second insulating member 72 assists the auxiliary potential terminal member 75 (different potential terminal member) in contact with the auxiliary potential pad 125 (different potential pad) of the ceramic element 100 in the second insertion hole 72d. The potential terminal member 75 is held. 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 ceramic 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 ceramic element 100 in the second insertion hole 72d. Yes. At the same time, the second insulating member 72 electrically insulates the auxiliary potential terminal member 75, the first heater terminal member 76, and the second heater terminal member 77 from the inner cylinder 80.

Further, the discharge potential terminal member 73 is connected to one end portion 161 t of the discharge potential lead wire 161 in the first insertion hole 72 c of the second insulating member 72. Thereby, the discharge potential terminal member 73 is set to the discharge potential PV2.
In addition, in the second insertion hole 72d of the second insulating member 72, the auxiliary potential terminal member 75 is connected to one end portion 162t of the auxiliary potential lead wire 162 (different potential lead wire). Thereby, the auxiliary potential terminal member 75 is set to the auxiliary potential PV3. 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. 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. As a result, the second heater terminal member 77 is set to the chassis GND potential CGND.

  A distal end portion 82s of the sensor GND connection fitting 82 is fitted on the base end portion 80k of the inner cylinder 80, and is laser welded. Further, electric wires 165 to 168 are inserted into the sensor GND connection fitting 82. Of the outer conductors 165G and 166G of the electric wires 165 and 166, the inner outer conductors 165G1 and 166G1 are electrically connected to the sensor GND connection fitting 82. As a result, the inner cylinder 80, the metal shell 50, the inner protector 45, and the outer protector 40 that are electrically connected to the sensor GND connection fitting 82 are all set to the sensor GND potential SGND (first reference potential).

  Further, in the outer cylinder 95, a fluoro rubber grommet 84 and a chassis GND connection fitting 83 are disposed in the small-diameter portion 96 on the base end side GK, and the electric wires 165 to 168 are inserted through these. . Of the outer conductors 165G and 166G of the electric wires 165 and 166, the outer outer conductors 165G2 and 166G2 are electrically connected to the chassis GND connection fitting 83, respectively.

  The chassis GND connection fitting 83 is crimped inward in the radial direction together with the small diameter portion 96 of the outer cylinder 95. Thus, the grommet 84 and the chassis GND connection fitting 83 are fixed in the small diameter portion 96 of the outer cylinder 95. As a result, the fitting 90, the outer cylinder 95, and the chassis GND connection fitting 83 that are electrically connected to the exhaust pipe EP and the attachment boss BO are all set to the chassis GND potential CGND that is insulated from the sensor GND potential SGND. Further, as described above, the chassis GND potential CGND is made common with the GND potential of the battery BT (see FIG. 4) mounted on the vehicle AM.

  Next, the ceramic element 100 (sensor element) will be described in detail. As shown in FIGS. 5 and 6, the ceramic element 100 has a plate shape extending in the axial direction GH and includes a ceramic base 101 (insulating base) made of an electrical insulating material (specifically alumina). In the ceramic substrate 101, a discharge electrode body 110, an auxiliary electrode body 120, and a heater portion 130 are embedded and integrally sintered.

  More specifically, the ceramic substrate 101 has three ceramic layers 102, 103, and 104 made of alumina derived from an alumina green sheet, and two insulating coatings made of alumina formed by printing between these layers. Layers 105 and 106 are interposed. A discharge electrode body 110 is disposed between the insulating coating layer 105 and the ceramic layer 103. Further, an auxiliary electrode body 120 is disposed between the ceramic layer 103 and the insulating coating layer 106. Further, a heater unit 130 is disposed between the insulating coating layer 106 and the ceramic layer 104. And these are integrated and the ceramic element 100 (sensor element) is formed.

  In the present embodiment, the ceramic base 101 (insulating base) of the ceramic element 100 has an axis line on the first ceramic portion 101A composed of the ceramic layers 103 and 104 rather than the ceramic layers 103 and 104, as shown in FIG. The second ceramic portion 101B made of the ceramic layer 102, in which the length in the direction GH is shortened, is stacked. In addition, the second tip 101BS located on the tip side GS in the axial direction GH in the second ceramic portion 101B is more axial in the axial direction than the first tip 101AS located on the tip side GS in the axial direction GH in the first ceramic portion 101A. It is pulled down to the base end side GK of GH.

  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. Furthermore, the ceramic element 100 has a discharge potential pad 113 that is electrically connected to the lead portion 111 of the discharge electrode body 110. The lead portion 111 and the discharge potential pad 113 are integrally formed on one surface 103S1 of the ceramic layer 103 by pattern printing. In addition, the lead portion 111 and the embedded portion 112A on the proximal end side GK of the needle electrode portion 112 are covered with the insulating coating layer 105 and the ceramic layer 102, and the ceramic base body 101 (specifically, ceramic) Embedded between the layer 102 and the ceramic layer 103). That is, the ceramic substrate 101 includes the lead portion 111 and the embedded portion 112 </ b> A of the needle electrode portion 112 in the discharge electrode body 110.

  On the other hand, the exposed portion 112B on the tip side GS of the needle-like electrode portion 112 made of platinum wire is exposed from the second tip 101BS of the second ceramic portion 101B (see FIG. 5). Moreover, the needle-like tip 112S that is tapered on the tip side GS of the exposed portion 112B is bent so that its tip is separated from the surface 103S1 of the ceramic layer 103 by 2 to 3 mm (thus, the surface 103S1 of the ceramic layer 103). And projecting into the air outside the ceramic substrate 101.

  The discharge potential pad 113 is formed on the first main surface 101S1 (on the surface 103S1 of the ceramic layer 103) at the base end portion 101K located on the base end side GK in the axial direction GH of the ceramic base 101. As described above, the discharge potential pad 113 is brought into contact with the discharge potential pad 113 to be conductive.

  The auxiliary electrode body 120 is formed on the surface 103S2 of the ceramic layer 103 opposite to the surface 103S1 by pattern printing. The auxiliary electrode body 120 is disposed on the distal end side GS of the ceramic element 100 and has a rectangular auxiliary electrode part 122, and the auxiliary electrode that is connected to the auxiliary electrode part 122 and extends to the proximal end side GK of the ceramic element 100. A lead part 121 is provided. The auxiliary electrode body 120 (auxiliary electrode lead portion 121 and auxiliary electrode portion 122) is covered with an insulating coating layer 106 and is disposed in the ceramic base 101 (specifically, between the ceramic layer 103 and the ceramic layer 104). Buried.

  In addition, the auxiliary electrode part 122 of the auxiliary electrode body 120 includes the inside (ceramic layer 103) of the first ceramic part 101 </ b> A of the ceramic base 101 on the tip side GS in the axial direction GH with respect to the second tip 101 </ b> BS of the second ceramic part 101 </ b> B. Embedded between the ceramic layer 104 and the ceramic layer 104.

  On the other hand, the auxiliary electrode lead portion 121 of the auxiliary electrode body 120 is electrically connected to the conductive pattern 124 formed on the one surface 104S1 of the ceramic layer 104 from the end portion 123 on the base end side GK through the through hole 106c of the insulating coating layer 106. doing. Further, the conductive pattern 124 is formed on the other surface 104S2 of the ceramic layer 104 (that is, on the second main surface 101S2 at the base end portion 101K of the ceramic base 101) through the through hole 104h1 penetrating the ceramic layer 104. The auxiliary potential pad 125 is electrically connected. As described above, the auxiliary potential pad member 75 is brought into contact with the auxiliary potential pad 125 to be conductive.

  On the one surface 104S1 of the ceramic layer 104, a heater unit 130 is formed by pattern printing. The heater unit 130 is disposed on the distal end side GS of the ceramic element 100 and heats the ceramic element 100, and two heaters that are connected to the heat generation unit 131 and extend to the proximal end side GK of the ceramic element 100. Lead portions 132 and 133 are provided. The heater portion 130 is formed on one surface 104S1 of the ceramic layer 104 and is covered with the insulating coating layer 106.

  Further, the heater lead portion 132 is provided on the other surface 104S2 of the ceramic layer 104 (that is, the second main surface of the ceramic substrate 101) from the end portion 134 on the base end side GK through the through hole 104h2 penetrating the ceramic layer 104. 101S2) is electrically connected to the first heater pad 136 formed above. Further, the heater lead portion 133 is electrically connected from the end portion 135 on the base end side GK to the second heater pad 137 formed on the other surface 104S2 of the ceramic layer 104 through the through hole 104h2 penetrating the ceramic layer 104. doing. As described above, the first heater terminal member 76 is brought into contact with the first heater pad 136 to conduct therethrough. Further, the second heater pad member 137 is in contact with the second heater terminal member 77 to be conducted.

Next, particle detection by the particle detection system 1 will be described.
The discharge electrode body 110 of the ceramic 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. 4). Further, the auxiliary electrode body 120 is connected to the auxiliary electrode power supply circuit 240 of the control device 200 through the auxiliary potential lead wire 162. Further, the heater unit 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 (see FIG. 4).

  The outer conductors 165G1 and 166G1 inside the electric wires 165 and 166 are also connected to the first output terminal 211 of the ion source power circuit 210 and the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240 in the control device 200, The sensor GND potential is SGND (first reference potential). Furthermore, the inner protector 45 disposed around the ceramic element 100 is also set to the sensor GND potential SGND (first reference potential) via the sensor GND connection fitting 82 and the like conducted to the outer conductors 165G1 and 166G1.

  Here, a positive high voltage is applied to the needle electrode portion 112 of the discharge electrode body 110 from the ion source power supply circuit 210 of the control device 200 through the discharge potential lead wire 161, the discharge potential terminal member 73, and the discharge potential pad 113. A discharge potential PV2 (for example, 1 to 2 kV) (see FIG. 4) is applied. Then, between the needle-like tip 112S of the exposed portion 112B of the needle-like electrode 112 and the inner protector 45 (first member) that is set to the sensor GND potential SGND (first reference potential), air discharge ( Specifically, corona discharge is generated, and ions CP (positive ions) are generated around the needle-like tip 112S (see FIG. 7).

  As described above, the exhaust gas EG is taken into the inner protector 45 by the action of the outer protector 40 and the inner protector 45, and the intake exhaust gas from the proximal end GK toward the distal end GS near the ceramic element 100. EGI airflow is generated. Therefore, the generated ions CP adhere to the fine particles S in the intake exhaust gas EGI as shown in FIG. Thereby, the fine particles S become positively charged charged fine particles SC, and flow toward the discharge port 45O together with the intake exhaust gas EGI and are discharged.

  On the other hand, the auxiliary electrode unit 122 of the auxiliary electrode body 120 has a predetermined potential (for example, from the auxiliary electrode power circuit 240 of the control device 200 through the auxiliary potential lead wire 162, the auxiliary potential terminal member 75, and the auxiliary potential pad 125. , An auxiliary potential PV3 of 100 to 200 V is applied (see FIG. 4). Thereby, the repulsive force which goes to the inner side protector 45 (collection pole) of the radial direction outer side from the auxiliary electrode part 122 is given to the floating ion CPF (refer FIG. 7) which did not adhere to microparticles | fine-particles S among the produced | generated ions CP. . Thereby, floating ion CPF is made to adhere to each part of a collection pole (inner protector 45), and collection is assisted. Thus, the floating ions CPF can be reliably collected, and even the floating ions CPF are prevented from being discharged from the discharge port 45O.

  In the system 1, the signal current detection circuit 230 detects a signal (signal current Is) corresponding to the charge amount of the discharged ions CPH adhering to the charged fine particles SC discharged from the discharge port 45O. The signal current Is flows between the sensor GND potential SGND (the potential of the inner 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 this embodiment, the inner protector 45 around the ceramic element 100 is set to the sensor GND potential SGND, and corona discharge is generated between the needle electrode portion 112 of the discharge electrode body 110. Further, the inner protector 45 is also used as a collecting electrode for collecting floating ions CPF. That is, in this embodiment, the collection potential for collecting the floating ions CPF by the inner protector 45 (collection electrode) is equal to the sensor GND potential SGND.

  Further, in the present system 1, the first heater lead wire 163 and the first heater terminal member 76, and the second heater lead wire 164 and the second heater terminal member 77 from the heater energization circuit 226 of the measurement control circuit 220 of the control device 200. Then, a predetermined heater energization voltage is applied between the first heater pad 136 and the second heater pad 137. Then, the heat generating part 131 of the heater part 130 generates heat by energization, heats the ceramic element 100, and can remove foreign matters such as water droplets and soot adhered to the ceramic element 100. Thereby, the electrical insulation of the ceramic element 100 can be recovered or maintained.

  In this embodiment, a voltage obtained by pulse-controlling a 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 as the heater energization voltage. 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. 4). reference).

  Incidentally, in the fine particle sensor 510 described above, the outer surface 471b of the first insulating member 471 is in contact with the inner peripheral surface 480c of the inner cylinder 480 (see FIG. 11). Therefore, when the surface of the first insulating member 471 is deteriorated due to water droplets adhering to the surface of the first insulating member 471 or the first insulating member 471 having a high temperature, the first insulating member There is a possibility that discharge (spark discharge) or current leakage may occur between the discharge potential terminal member 473 (discharge potential) and the inner cylinder 480 (first reference potential) through the surface of the member 471.

  Specifically, the inner side surface 471 f of the first insulating member 471 has an inner contact portion 471 h that contacts the discharge potential terminal member 473. The inner contact portion 471h includes an innermost frontmost contact portion 471n located on the most distal side GS in the axial direction GH (see FIG. 13). In addition, the outer surface 471 b of the first insulating member 471 has an outer contact portion 471 v that contacts the inner peripheral surface 480 c of the inner cylinder 480. The outer contact portion 471v has an outermost distal contact portion 471w located on the most distal side GS in the axial direction GH. Therefore, for example, as shown in FIG. 13, in the creeping path CR from the inner contact portion 471 h to the outer contact portion 471 v through the surface of the first insulating member 471, the inner most distal contact portion 471 n to the outer most distal contact portion 471 w. There is a possibility that spark discharge may occur between the discharge potential terminal member 473 and the inner cylinder 480 in the shortest creepage path SCR leading to the front end. When such discharge (spark discharge) or current leak occurs, there is a possibility that fine particles in the gas to be measured cannot be detected properly.

On the other hand, in the particle sensor 10 of the present embodiment, the distal end portion 71s of the first insulating member 71 (the portion located on the most distal end side GS of the first insulating member 71) is in the radial direction of the first insulating member 71. It is located outside the innermost cutting edge contact portion 71n and is positioned closer to the tip side GS than the inner cutting edge contact portion 71n in the axial direction GH (see FIGS. 8 and 9). The tip 71s has a cylindrical shape (see FIG. 8).
Further, the proximal end portion 71k of the first insulating member 71 (the portion of the first insulating member 71 located closest to the proximal end GK) is more than the innermost proximal end contact portion 71y in the radial direction of the first insulating member 71. It is located on the outer side and is located on the base end side GK from the innermost base end contact portion 71y in the axial direction GH (see FIGS. 8 and 9). The base end portion 71k has a cylindrical shape.

Furthermore, the first insulating member 71 is outside the distal end portion 71s in the radial direction of the first insulating member 71, and is closer to the base end side GK (upper side in FIG. 9) than the inner most distal contact portion 71n in the axial direction GH. The outer contact portion 71v (the portion of the outer surface 71b of the first insulating member 71 that contacts the inner peripheral surface 80c of the inner cylinder 80) is provided at the position. In addition, the outer contact portion 71v is outside the proximal end portion 71k in the radial direction of the first insulating member 71, and is more distal than the innermost proximal end contact portion 71y in the axial direction GH (lower side in FIG. 9). Side).
More specifically, the outer surface 71b of the first insulating member 71 is centered in the axial direction GH (specifically, on the proximal end side GK with respect to the innermost distal contact portion 71n and on the innermost proximal contact portion 71y). A cylindrical central portion located at a position closer to the tip side GS) has a stepped cylindrical shape protruding outward in the radial direction from other portions. And the cylindrical center part of the outer surface 71b is taken as the outer side contact part 71v (site | part which contacts the internal peripheral surface 80c of the inner cylinder 80).

As shown in FIG. 9, the first insulating member 71 having such a configuration has an inner most distal contact portion 71n in the creeping path CR from the inner contact portion 71h to the outer contact portion 71v through the surface of the first insulating member 71. The shortest creepage path SCR on the tip side from the outermost distal contact portion 71w is “the side on which the outermost distal contact portion 71w is located in the axial direction GH (vertical direction in FIG. 9 as viewed from the innermost distal contact portion 71n) ( In the present embodiment, a first via point P1 (distal end portion) located on the side opposite to the proximal end side GK (that is, the side away from the outermost distal contact portion 71w in the axial direction GH, in this embodiment, the distal end side GS). The tip side detour route SD1 via “point located at the tip of 71s)” is included.
Therefore, in the fine particle sensor 10 of the present embodiment, the tip of the first insulating member is compared with a case where the tip side shortest creepage path does not include the above-described bypass path (tip side bypass path). The tip side shortest creeping route SCR can be lengthened by the length of the side detour route SD1.

Further, as shown in FIG. 9, the first insulating member 71 of the above-described form has the shortest creepage path KCR on the base end side from the innermost proximal contact portion 71 y to the outermost proximal contact portion 71 x, “the innermost proximal base. When viewed from the end contact portion 71y, in the axial direction GH (vertical direction in FIG. 9), the side (the distal end side GS in the present embodiment) opposite to the side where the outermost proximal contact portion 71x is located (that is, the axial direction GH). About the third end point P3 (a point located at the base end of the base end portion 71k) located on the side farthest from the outermost base end contact portion 71x, the base end side GK in this embodiment) The route KD1 is included.
Therefore, in the fine particle sensor 10 of the present embodiment, the first insulating member 71 is configured such that the detour path (proximal end detour path) as described above is not included in the shortest creepage path KCR on the proximal end side. In comparison, the base end side shortest creeping path KCR can be lengthened by the length of the base end side detour path KD1.

  As described above, in the fine particle sensor 10 of the present embodiment, water droplets adhere to the surface of the first insulating member 71 or the temperature of the first insulating member 71 becomes high. Even when the insulating property is lowered, discharge and current leakage between the discharge potential terminal member 73 and the inner cylinder 80 through the surface of the first insulating member 71 are less likely to occur.

  Furthermore, in the particle sensor 10 of the present embodiment, the inner cylinder 80 has a fixing portion 80d that fixes the second insulating member 72 and the first insulating member 71 while being in contact with the second insulating member 72 (see FIG. 8). . Specifically, as shown in FIG. 8, the fixing portion 80 d is a proximal end portion of the proximal end portion 80 k of the inner cylinder, and a flange portion 72 f (a portion that bulges radially outward) of the second insulating member 72. ) And the second fixing portion 80j that is crimped so as to be bent radially inward and that contacts the base end surface 72h of the flange portion 72f of the second insulating member 72. Have.

  Furthermore, an insertion hole 71j into which a distal end portion 72s that is a portion of the distal end side GS of the second insulating member 72 is inserted is formed in the proximal end portion 71k located on the proximal end side GK of the first insulating member 71. (See FIGS. 3 and 8). The insertion hole 71j has a stepped shape, and an inner peripheral surface 71g with which the outer peripheral surface of the distal end portion 72s of the second insulating member 72 contacts and an abutting surface 71m with which the distal end surface 72t of the second insulating member 72 abuts. (See FIG. 3).

  Furthermore, an insertion hole 71p into which the proximal end portion 70k of the insulating holder 70 is inserted is formed in the distal end portion 71s located on the distal end side GS of the first insulating member 71 (see FIGS. 3 and 8). The insertion hole 71p has a step shape, and has an inner peripheral surface 71q with which the outer peripheral surface of the base end portion 70k of the insulating holder 70 contacts, and a contact surface 71r with which the base end surface 70t of the insulating holder 70 contacts. (See FIG. 8). Further, the front end surface 70 f of the insulating holder 70 is in contact with the ceramic sleeve 56 fixed in the metal shell 50.

  Accordingly, the second insulating member 72, the first insulating member 71, and the insulating holder 70 that are disposed adjacent to (in contact with) the axial direction GH include the second fixing portion 80j of the inner cylinder 80 and the ceramic sleeve 56. And is fixed in the axial direction GH.

Further, the second insulating member 72 is fixed in the radial direction (a direction orthogonal to the axial direction GH) by the first fixing portion 80 h of the inner cylinder 80. Furthermore, since the distal end portion 72s of the second insulating member 72 is inserted into the insertion hole 71j of the first insulating member 71, the inner peripheral surface 71g constituting the insertion hole 71j of the first insulating member 71 is The first insulating member 71 is also fixed in the radial direction in such a manner that it contacts the outer peripheral surface of the distal end portion 72 s of the two insulating member 72. Further, since the base end portion 70k of the insulating holder 70 is inserted into the insertion hole 71p of the first insulating member 71, the outer peripheral surface of the base end portion 70k of the insulating holder 70 is inserted into the first insulating member 71. The insulating holder 70 is also fixed in the radial direction in such a manner that it contacts the inner peripheral surface 71q constituting the hole 71p.
In this way, in the fine particle sensor 10 of the present embodiment, the first insulating member 71 is formed in the inner cylinder 80 (cylindrical body) not only in the radial direction (the direction orthogonal to the axial direction GH) but also in the axial direction GH. It can be appropriately fixed.

(Deformation)
Next, modifications of the present invention will be described. The particle sensor 310 of the present modification is different from the particle sensor 10 of the embodiment only in the shape of the first insulating member, and the other is the same.

In the fine particle sensor 310 of the present modified embodiment, as shown in FIG. 10, the distal end portion 371 s of the first insulating member 371 (the portion located on the most distal end side GS of the first insulating member 371) is the first insulating member 371. It is located outside the inner most advanced contact portion 371n in the radial direction and on the tip side GS (lower side in FIG. 10) than the inner most advanced contact portion 371n in the axial direction GH. The tip 371s has a cylindrical shape.
Further, the proximal end portion 371k of the first insulating member 371 (the portion of the first insulating member 371 located on the most proximal side GK) is more than the innermost proximal end contact portion 371y in the radial direction of the first insulating member 371. It is located on the outer side and on the base end side GK (upper side in FIG. 10) than the innermost base end contact portion 371y in the axial direction GH. The base end portion 371k has a cylindrical shape.

Furthermore, the first insulating member 371 is located on the outer side of the distal end portion 371s in the radial direction of the first insulating member 371 and on the distal end side GS (lower side in FIG. ) And at the position of the base end side GK with respect to the distal end 371 ss of the distal end portion 371 s, the outer most distal contact portion 371 w is provided.
Furthermore, the first insulating member 371 is located outside the proximal end portion 371k in the radial direction of the first insulating member 371, and is located closer to the proximal end side GK (in FIG. 10) than the innermost proximal end contact portion 371y in the axial direction GH. The outermost proximal end contact portion 371x is located on the distal side GS relative to the proximal end 371kk of the proximal end portion 371k.

  More specifically, the outer side surface 371b of the first insulating member 371 is a portion (tip side portion 371b1) located on the tip side GS in the axial direction GH (specifically, the tip side GS with respect to the innermost tip contact portion 371n). ) And the base end side GK (specifically, the base end side portion 371b2) positioned at the base end side contact portion 371y and the portion located at the base end side 371b2 It has a cylindrical shape with a level difference projecting radially outward from the side portion 371b1 and the base end side portion 371b2. And the cylindrical intermediate part of the outer side surface 371b is taken as the outer side contact part 371v (site | part which contacts the internal peripheral surface 80c of the inner cylinder 80).

As shown in FIG. 10, the first insulating member 371 having such a configuration has an inner most distal contact portion 371 n in the creeping path CR from the inner contact portion 371 h to the outer contact portion 371 v through the surface of the first insulating member 371. The shortest creepage path SCR on the distal end side extending from the outermost distal contact portion 371w is “the side on which the innermost distal contact portion 371n is located in the axial direction GH (vertical direction in FIG. 10 as viewed from the outermost distal contact portion 371w) ( In the present embodiment, the second via point P2 (first side) located on the opposite side to the base end side GK (that is, the side away from the inner most distal contact portion 371n in the axial direction GH, in this embodiment, the front end side GS). This includes the tip-side detour path SD <b> 2 via “the point located at the tip 371 ss of the insulating member 371”).
Therefore, in the fine particle sensor 310 of the present modified embodiment, the tip of the first insulating member is compared to a case where the tip-side shortest creepage path does not include the above-described bypass path (tip-side bypass path). The tip side shortest creeping route SCR can be lengthened by the length of the side detour route SD2.

Further, as shown in FIG. 10, the first insulating member 371 having the above-described configuration has the shortest creepage path KCR on the base end side from the innermost proximal contact portion 371y to the outermost proximal contact portion 371x as “the outermost proximal base. When viewed from the end contact portion 371x, the side where the innermost proximal contact portion 371y is located in the axial direction GH (vertical direction in FIG. 10) (the distal end side GS in the present modified embodiment) is the opposite side (that is, the axial direction GH). The fourth end point P4 (the point located at the base end 371kk of the first insulating member 371) located on the side farthest from the innermost base end contact portion 371y, in this embodiment, the base end side GK) " This includes the side detour route KD2.
Therefore, in the particulate sensor 310 of the present modified embodiment, the first insulating member 371 is configured such that the detour path (proximal end detour path) as described above is not included in the shortest creepage path KCR on the proximal end side. In comparison, the shortest creepage path KCR on the base end side can be lengthened by the length of the bypass path KD2 on the base end side.

  As described above, in the fine particle sensor 310 of the present modified embodiment, water droplets adhere to the surface of the first insulating member 371 or the temperature of the first insulating member 371 becomes high. Even when the insulating property is lowered, discharge and current leakage between the discharge potential terminal member 73 and the inner cylinder 80 through the surface of the first insulating member 371 are less likely to occur.

In the above, the present invention has been described with reference to the embodiments and modifications. However, the present invention is not limited to the above-described embodiments and the like, and can be applied with appropriate modifications without departing from the gist thereof. Not too long.
For example, in the embodiment and the modification, the discharge potential PV2 is a positive high potential, but the discharge potential PV2 may be a negative high potential.

  In the embodiment and the modification, the ceramic base 101 (insulating base) made of alumina encloses the embedded portion 112A of the discharge electrode body 110 as the ceramic element 100 (sensor element). However, the structure in which the discharge electrode body is provided on the insulating base in the sensor element is not limited to this. For example, a discharge electrode body is formed on the surface of a substrate made of an insulating ceramic such as alumina by printing or the like, and a part thereof is glass coated to form an embedded portion, whereby an insulating substrate made of a ceramic substrate and a glass coat. A ceramic element (sensor element) provided with a discharge electrode body may be used.

  Further, in the embodiment and the modification, the first insulating members 71 and 371 are configured by one member, but may be configured by a plurality of members. As a form constituted by a plurality of members, for example, a cylindrical inner member located radially inside and a cylindrical outer member located radially outside are formed, and the outer peripheral surface of the inner member is covered with the outer member. The form which was made is mentioned.

1 Particle detection system 10, 310 Particle sensor 40 Outer protector 45 Inner protector (first member)
50 metal shells 71 and 371 first insulating members 71b and 371b outer side surfaces 71f and 371f inner side surfaces 71h and 371h inner contact portions 71n and 371n inner most distal contact portions 71y and 371y innermost proximal end contact portions 71v and 371v outer contact portions 71w , 371w Outer most advanced contact portion 71x, 371x Outer most proximal end contact portion 72 Second insulating member 73 Discharge potential terminal member 75 Auxiliary potential terminal member (different potential terminal member)
76 First heater terminal member 77 Second heater terminal member 80 Inner cylinder (tubular body)
80c Inner peripheral surface 80d Fixed part 100 Ceramic element (sensor element)
100P Discharge pad portion 100R Different potential pad portion 101 Ceramic substrate (insulating substrate)
110 Discharge electrode body 113 Discharge potential pad 120 Auxiliary electrode body 125 Auxiliary potential pad (different potential pad)
130 heater portion 136 first heater pad 137 second heater pad 161 discharge potential lead wire 162 auxiliary potential lead wire (different potential lead wire)
163 First heater lead wire 164 Second heater lead wire 200 Controller 210 Ion source power supply circuit 220 Measurement control circuit 226 Heater energization circuit 230 Signal current detection circuit 240 Auxiliary electrode power supply circuit CGND Chassis GND potential EG Exhaust gas (measured gas)
EP Exhaust pipe GH Axial direction GS Tip side GK Base side PV2 Discharge potential PV3 Auxiliary potential (different potential)
PVht First heater potential S Fine particle SGND Sensor GND potential (first reference potential)
CR Creepage path SCR Tip side shortest creepage path SD1, SD2 Tip side detour path P1 First waypoint P2 Second waypoint P3 Third waypoint P4 Fourth waypoint KCR Base end side shortest creepage route KD1, KD2 Base end side detour Route

Claims (2)

A first member having a first reference potential;
An insulating base made of an electrical insulating material and extending in the axial direction,
A discharge electrode body provided on the insulating substrate, wherein a discharge potential higher than the first reference potential is applied to generate an air discharge between the first member and the discharge electrode body; ,
A sensor element having a discharge potential pad formed on the surface of the insulating substrate in conduction with the discharge electrode body and having the discharge potential.
A particulate sensor having a form extending from a proximal end side in the axial direction to a distal end side,
A discharge potential terminal member connected to the discharge potential lead wire and having the discharge potential;
A cylindrical body made of metal and extending in the axial direction, which is electrically connected to the first member and used as the first reference potential;
A first insulating member made of an electrical insulating material and extending in the axial direction and positioned inside the cylindrical body, the discharge pad portion where the discharge potential pad is located among the sensor elements, and the above The discharge potential terminal member is accommodated inside the first insulating member, the discharge potential terminal member is held while the discharge potential terminal member is in contact with the discharge potential pad, and the discharge potential terminal member and the cylindrical body are held. A first insulating member that electrically insulates between,
The inner surface of the first insulating member has an inner contact portion that comes into contact with the discharge potential terminal member,
The inner contact portion is an inner most distal contact portion located on the most distal side in the axial direction among the inner contact portions, and an innermost proximal contact portion located on the most proximal side in the axial direction, Have
The outer surface of the first insulating member has an outer contact portion that comes into contact with the inner peripheral surface of the cylindrical body,
The outer contact portion is an outermost distal contact portion located closest to the distal end in the axial direction among the outer contact portions, and an outermost proximal contact portion located closest to the proximal end in the axial direction. Have
The first insulating member is
Of the creeping paths from the inner contact part to the outer contact part through the surface of the first insulating member, the tip-side shortest creepage path from the inner leading edge contact part to the outer leading edge contact part is the inner leading edge. When viewed from the contact portion, the first via point located on the side opposite to the side on which the outer most distal contact portion is located in the axial direction, or the inner side in the axial direction when viewed from the outer most distal contact portion. Including a tip-side detour route via a second via point located on the opposite side to the side where the most advanced contact portion is located, and
Of the creeping paths, the shortest creepage path on the base end side from the innermost proximal contact part to the outermost proximal contact part is the outermost base in the axial direction as viewed from the innermost proximal contact part. When viewed from the third via point located on the opposite side to the side on which the end contact portion is located or the outermost proximal contact portion, the side opposite to the side on which the innermost proximal contact portion is located in the axial direction The particulate sensor which makes the form containing the base end side detour route which passes along the 4th waypoint located in the side. The fine particle sensor according to claim 1,
The sensor element is
A different potential pad formed on the surface of the insulating substrate and having a different potential from the discharge potential;
The particulate sensor
A different potential terminal member connected to a different potential lead wire and having the different potential;
A second insulating member made of an electrical insulating material and extending in the axial direction and adjacent to the first insulating member in the axial direction, wherein the different potential pad of the sensor element is located. A potential pad portion and the different potential terminal member housed in the second insulating member, and a second insulating member holding the different potential terminal member while contacting the different potential terminal member to the different potential pad; Prepared,
The cylindrical body is a particulate sensor having a fixing portion that contacts the second insulating member and fixes the second insulating member and the first insulating member in the axial direction.

Images