JP6506703B2 - Particle detection system - Google Patents

Description

  The present invention relates to a particle detection system, and more particularly to a particle detection system for detecting particles contained in a gas to be measured flowing in a vent pipe.

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

  Such a particulate detection system includes, for example, a particulate sensor attached to an exhaust pipe at ground potential, and a sensor driving unit that drives the particulate sensor. The particulate sensor comprises, for example, an inner fitting having a gas intake pipe, an outer fitting, and an insulating spacer. Among these, the inner metal fitting is a member which is at a first potential different from the ground potential and takes in the exhaust gas into the gas inlet pipe. The outer metal fitting is a cylindrical member that surrounds the radial direction of the inner metal fitting and is attached to the exhaust pipe to be at a ground potential. The insulating spacer is a cylindrical member which is interposed between the inner and outer metal fittings to electrically insulate them from each other. Such a particle detection system is disclosed, for example, in Patent Documents 1 and 2.

JP, 2014-10099, A JP, 2015-129712, A

  By the way, in the case where the above-mentioned insulating spacer has the exposed portion in the sensor exposed in the sensor internal space surrounded by the outer fitting at the outside of the exhaust pipe, the following may occur. Specifically, for example, during operation of the internal combustion engine, the particulate sensor becomes high temperature by being heated by the high temperature exhaust gas. Exhaust gas contains a large amount of water (water vapor), and this water (water vapor) may leak into the sensor internal space during operation of the internal combustion engine. On the other hand, when the operation of the internal combustion engine is stopped, the particulate sensor is cooled by the outside air. Therefore, for example, when the outside air temperature is low, dew condensation may occur on the surface of the exposed portion in the sensor of the insulating spacer after the operation of the internal combustion engine is stopped.

  When water (water generated by condensation) adheres to the surface of the exposed portion in the sensor of the insulating spacer, the insulation of the surface of the exposed portion in the sensor is reduced. As a result, the insulation between the inner fitting that is at the first potential and the outer fitting that is at the ground potential is reduced. In such a state, when the particulate matter is detected by driving the particulate matter sensor by the sensor driving unit, there is a possibility that the amount of the particulates in the exhaust gas (gas to be measured) can not be appropriately detected.

  The present invention has been made in view of the present situation, and an object of the present invention is to provide a particle detection system capable of appropriately detecting the amount of particles contained in a measurement gas.

  One embodiment of the present invention is a particle detection system for detecting particles contained in a gas to be measured flowing in a vent pipe, comprising a particle sensor mounted on the vent pipe at ground potential and a sensor for driving the particle sensor. A driving means, the particulate sensor being mounted on the vent pipe and having a cylindrical outer metal fitting that is brought to the ground potential, and a first electric potential that is different from the ground potential, the radial direction by the outer metal fitting And a cylindrical insulating spacer interposed between the inner bracket and the outer bracket to electrically insulate between the inner bracket and the outer bracket. The insulating spacer is an outer portion of the vent pipe. An exposed portion in the sensor exposed in the sensor inner space surrounded by the outer bracket, and a heater for heating the exposed portion in the sensor, wherein the heater is an inner portion of the insulating spacer Insulating inspection means for inspecting whether the degree of insulation between the inner metal fitting and the outer metal fitting is within an allowable range, including the embedded heating resistor, wherein the particulate matter detection system comprises: A heater-energizing means for generating heat by heating the heat-generating resistor, wherein the heater-energizing means determines that the insulation degree is not within the allowable range by the insulation inspection means. The first heater is energized to energize the heater for a predetermined first time during which water adhering to the surface of the exposed portion in the sensor is expected to be removed, and the sensor drive unit is configured to It is a particulate matter detection system which drives the particulate matter sensor after it is determined that the degree of insulation falls within the allowable range, or after the first heater energization is finished.

  In the particle detection system described above, the insulation inspection means inspects whether the degree of insulation between the inner and outer metal fittings is within an acceptable range. Specifically, for example, a predetermined voltage is applied between the inner and outer brackets, and the magnitude of the leakage current flowing between the inner and outer brackets is measured, and the magnitude of the leakage current is within an allowable range. It is determined whether it is inside (for example, it is below the preset threshold). In this case, the "degree of insulation" is indicated by the magnitude of the leakage current.

  In addition, the tolerance | permissible_range of the insulation grade between an inner metal fitting and an outer metal fitting is set in the range of the insulation grade which can detect appropriately the quantity of the microparticles | fine-particles in to-be-measured gas by a particle detection system. . When water droplets generated by condensation (hereinafter, also referred to as dew condensation water) adhere to the surface of the exposed portion of the insulating spacer in the sensor, the degree of insulation between the inner and outer metal fittings is not within the allowable range It can be determined that

  Furthermore, in the particle detection system described above, when it is determined by the insulation inspection means that the degree of insulation is not within the allowable range, the heater conduction means performs the first heater conduction. Specifically, the heater energizing means energizes the heater for a predetermined first time (for example, 5 minutes) in which water adhering to the surface of the exposed portion in the sensor is expected to be removed. Thereby, the dew condensation water adhering to the surface of the exposure part in a sensor can be removed (evaporated).

  Furthermore, in the particle detection system described above, the sensor drive unit drives the particle sensor after the insulation inspection unit determines that the insulation degree is within the allowable range, or after the first heater is energized. Do.

That is, if it is determined by the insulation inspection means that the degree of insulation is within the allowable range, then the sensor drive means drives the particle sensor to detect the amount of particles. Thereby, the amount of particulates in the gas to be measured can be appropriately detected.
On the other hand, if it is determined by the insulation inspection means that the degree of insulation is not within the allowable range, the sensor drive means drives the particle sensor to detect the amount of particles after energization of the first heater is finished. Let Therefore, in the above-described particle detection system, after the dew condensation water is removed from the surface of the exposed portion in the sensor of the insulating spacer by the above-described first heater energization, the amount of particles is detected. Thereby, the amount of particulates in the gas to be measured can be appropriately detected.

  Further, in the above-described particulate sensor, the heater includes the heating resistor embedded inside the insulating spacer. That is, the heat generating resistor is disposed inside the insulating spacer. This can prevent the condensation water from adhering to the heat generating resistor. For this reason, it can suppress that electricity supply with respect to a heater can not be appropriately performed by dew condensation water adhering to a heat generating resistor, or a heat generating resistor degrades. Therefore, even when the particulate sensor is used for a long time, the heating performance by the heater can be maintained well.

  Furthermore, in the particulate matter detection system described above, the particulate matter sensor generates an aerial discharge by being driven by the sensor driving means, and ions generated by the aerial discharge are included in the measurement gas. The fine particles in the gas to be measured are attached to the fine particles to generate charged fine particles, and using a signal current flowing between the first potential and the ground potential according to the amount of the fine particles. The particle detection system may detect the amount of

  In the above-described particle detection system, the amount of particles in the gas to be measured is detected using the signal current flowing according to the amount of charged particles described above, so the signal current becomes very small. By the way, when dew condensation water adheres to the surface of the exposed portion in the sensor of the insulating spacer and the insulation of the surface of the exposed portion in the sensor is reduced, the inner metal fitting that is set to the first potential Leakage current may flow between the metal case and the outer metal fitting that is at ground potential. Depending on the magnitude of the leakage current, the signal current may not be properly detected.

  On the other hand, in the above-described particle detection system, as described above, after it is determined that the degree of insulation between the inner and outer metal fittings is within the allowable range, or in the sensor by the first heater energization. After the dew condensation water is removed from the surface of the exposed portion, the amount of particles is detected. Thus, in the particle detection system described above, the minute signal current can be appropriately detected without being affected by the leakage current, so the amount of particles contained in the gas to be measured can be detected appropriately.

  Furthermore, in any one of the above-mentioned particulate detection systems, the ventilation pipe is an exhaust pipe of an internal combustion engine, the measurement gas is an exhaust gas, and the insulation inspection unit is configured to operate the internal combustion engine. After starting, prior to the start of driving of the particulate sensor by the sensor driving means, particulates to check whether the degree of insulation between the inner and outer metal fittings is within the allowable range It is good if it is a detection system.

  According to the above-described particulate matter detection system, it is possible to appropriately detect the amount of particulate matter in the exhaust gas discharged from the internal combustion engine after the operation of the internal combustion engine is started.

It is a longitudinal cross-sectional view of the particulate matter sensor concerning an embodiment. FIG. 1 is an enlarged vertical cross-sectional view of the particle sensor as viewed from the side rotated 90 degrees around an axis. It is an exploded perspective view of a particulate sensor concerning an embodiment. 1 is a schematic view of a particle detection system according to an embodiment. It is a perspective view of the insulation spacer which concerns on embodiment. It is a longitudinal cross-sectional view of the same insulating spacer. It is the disassembled perspective view which expand | deployed the layered heater part of the same insulating spacer. It is a perspective view of a ceramic element concerning an embodiment. It is an exploded perspective view of the ceramic element. It is an explanatory view of a particulate sensor concerning an embodiment. It is a flowchart which shows the flow of the microparticles | fine-particles detection which concerns on embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view of a particle sensor 10 included in a particle detection system 1 according to the present embodiment. FIG. 2 is an enlarged cross-sectional view of the particle sensor 10, and FIG. 1 is an enlarged vertical cross-sectional view seen from the side rotated 90 degrees around the axis AX. FIG. 3 is an exploded perspective view of the particulate sensor 10. FIG. 4 is a schematic view of the particle detection system 1 according to the embodiment. However, in FIG. 4, the circuit unit 200 included in the particle detection system 1 is mainly illustrated, and only a part (the electric wire 161 or the like) of the particle sensor 10 is illustrated.

  In FIG. 1, in the longitudinal direction GH along the axis AX of the particle sensor 10, the side on the side where the gas inlet pipe 25 is disposed (downward in FIG. 1) is the tip side GS, and the electric wires 161, 163 etc. The side (upper side in FIG. 1) from which is extended is referred to as the proximal side GK.

  The particulate detection system 1 detects the amount of particulates S (such as soot) contained in exhaust gas (gas to be measured) EG flowing through an exhaust pipe (vent) of an internal combustion engine (engine). The particle detection system 1 is configured of a particle sensor 10 and a circuit unit 200 (see FIGS. 1 and 4).

  First, the particle sensor 10 will be described in detail. The particulate sensor 10 is attached to a metal exhaust pipe EP set to the ground potential PVE (see FIG. 1). Specifically, a gas intake pipe 25 which is a tip end portion of the inner metal fitting 20 of the particulate sensor 10 is disposed in the exhaust pipe EP through a mounting opening EPO provided in the exhaust pipe EP. Then, among the exhaust gas EG flowing in the exhaust pipe EP, the ion CP is made to adhere to the particulates S in the intake gas EGI taken into the gas intake pipe 25 from the gas intake port 65c to form charged microparticles SC. The gas is discharged to the exhaust pipe EP from the gas discharge port 60e together with the inflowing gas EGI (see FIG. 10).

  The particulate sensor 10 includes an inner fitting 20 having a gas intake pipe 25, an outer fitting 70, an insulating spacer 100, a ceramic element 120, six electric wires 161, 163, 171, 173, 175, 177, etc. (see FIG. 1 to 3)).

  Among them, the inner fitting 20 is electrically connected to the inner circuit case 250 or the like which is set to the first potential PV1 in the circuit unit 200 described later via the inner outer conductors 161g1 and 163g1 of the electric wires 161 and 163 described later, The first potential PV1 is different from the ground potential PVE. The inner fitting 20 includes a metal shell 30, an inner cylinder 40, an inner fitting 50, and a gas intake pipe 25 (an inner protector 60 and an outer protector 65).

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

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

  Further, the metal shell 30 has an externally threaded portion 30 n between the flange portion 31 and the tip portion 30 s. A spacer snap ring 32 is engaged with the male screw 30n to lock the insulating spacer 100 described later via the wire packing 39. Thus, the thick portion 101f of the spacer main body 101 of the insulating spacer 100 is sandwiched between the flange portion 31 of the metal shell 30 and the spacer retaining ring 32, and the metal shell 30 and the metal shell 30 and the insulating spacer 100 are interposed. The ceramic element 120 and the like held thereby are fixed to the mounting bracket 80.

  The inner cylinder 40 is a cylindrical stainless steel member extending in the longitudinal direction GH. The distal end portion 40s of the inner cylinder 40 is externally fitted to the proximal end side 30k of the metal shell 30, and laser welded to the proximal end side 30k.

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

  The first separator 44 is made of an insulator and has an insertion hole 44c. The ceramic element 120 is inserted into the insertion hole 44c, and the tip end portion of the discharge potential terminal 46 is accommodated. In the insertion hole 44c, the discharge potential terminal 46 is in contact with a later-described discharge potential pad 135 (see FIGS. 8 and 9) of the ceramic element 120.

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

  In addition to the element base end 120k of the ceramic element 120 being disposed in the second insertion hole 45d, the auxiliary potential terminal 47, the 2-1st heater terminal 48, and the 2-2nd heater terminal 49 are mutually insulated. Are housed in the Then, in the second insertion hole 45d, the auxiliary potential terminal 47 contacts the auxiliary potential pad 147 of the ceramic element 120, and the 2-1st heater terminal 48 contacts the 2-1st heater pad 156 of the ceramic element 120. The second 2-2 heater terminal 49 is in contact with the second 2-2 heater pad 158 of the ceramic element 120 (see FIGS. 1, 2, 8, and 9).

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

  The inner cylinder connection metal fitting 50 is a stainless steel member and is externally fitted to the base end 40k of the inner cylinder 40 while surrounding the base end side portion of the second separator 45, and the tip 50s of the inner cylinder connection metal fitting 50 is Laser welding is performed on the proximal end 40k of the inner cylinder 40. Four electric wires 161, 163, 173, 175 except the electric wires 171, 177 are inserted through the inner cylinder connection fitting 50, respectively. Among these, inner outer conductors 161g1 and 163g1 of electric wires 161 and 163 of a triple coaxial cable described later are connected to the inner cylinder connection fitting 50.

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

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

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

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

  Next, the outer bracket 70 will be described. As shown in FIGS. 1 and 3, the outer fitting 70 is cylindrical and made of metal, and the radial circumference of the inner fitting 20 is surrounded by the inner fitting 20 at a distance from the inner fitting 20, and the exhaust pipe is set to the ground potential PVE. It is attached to the EP and is set to the ground potential PVE. The outer fitting 70 includes a mounting fitting 80 and an outer cylinder 90.

  The mounting bracket 80 is a cylindrical, stainless steel member extending in the longitudinal direction GH. The mounting bracket 80 is disposed around the radial direction of the front end side portion of the metal shell 30 and the inner cylinder 40 in the inner bracket 20 so as to be separated therefrom. The mounting bracket 80 has a flange portion 81 which bulges outward in the radial direction to form an outer hexagonal shape. In addition, inside the mounting bracket 80, a stepped portion 83 having a stepped shape is provided. Further, a male screw (not shown) used for fixing to the exhaust pipe EP is formed on the outer periphery of the distal end side 80s of the mounting bracket 80 on the distal end side GS than the flange portion 81. The particle sensor 10 is attached to a metal mounting boss BO separately fixed to the exhaust pipe EP by an external thread of the tip side portion 80s, and is fixed to the exhaust pipe EP via the mounting boss BO (see FIG. See Figure 1).

  An insulating spacer 100 described later is disposed between the outer fitting 70 and the inner fitting 20, more specifically, between the mounting fitting 80 and the metal shell 30. The crimped portion 80 kk of the most proximal end GK of the mounting bracket 80 is crimped to the radially inner GDI, and the annular protrusion of the insulating spacer 100 is interposed through the wire packing 87, the pressing sleeve 110 and the powder filling body 115. The insulating spacer 100 is fixed to the mounting bracket 80 by pressing 103 against the front end side GS and pressing against the stepped portion 83 of the mounting bracket 80.

  The outer cylinder 90 is a cylindrical member extending in the longitudinal direction GH, and is a stainless steel member. The distal end portion 90s of the outer cylinder 90 is externally fitted to the proximal end side 80k of the mounting bracket 80, and is laser-welded to the proximal end side 80k. An outer cylinder connection fitting 95 is disposed in the small diameter portion 91 located on the proximal end GK of the outer cylinder 90, and a fluororubber grommet 97 is disposed on the proximal end GK. Six electric wires 161, 163, 171, 173, 175, and 177, which will be described later, are inserted into the outer cylinder connection fitting 95 and the grommet 97, respectively. Among these, outer outer conductors 161g2 and 163g2 of electric wires 161 and 163 of a triple coaxial cable to be described later are connected to the outer cylinder connection fitting 95, respectively. The outer cylinder connection fitting 95 is reduced in diameter radially inward by caulking together with the small diameter portion 91 of the outer cylinder 90, whereby the outer cylinder connection fitting 95 and the grommet 97 are fixed in the small diameter portion 91 of the outer cylinder 90. ing.

  When the particulate sensor 10 is mounted on the exhaust pipe EP, the internal space of the particulate sensor 10 surrounded by the outer metal fitting 70 (specifically, the outer cylinder 90) outside the exhaust pipe EP is a sensor internal space Assume SIS (see FIG. 1 and FIG. 2).

  Next, the insulating spacer 100 will be described. As shown in FIG. 5 and FIG. 6, the insulating spacer 100 is a cylindrical member extending in the longitudinal direction GH, and is a member mainly made of alumina. As described above, the insulating spacer 100 is interposed between the inner fitting 20 and the outer fitting 70 to electrically insulate the two. Specifically, it is disposed between the tip end portions of the metal shell 30 and the inner cylinder 40 of the inner metal fitting 20 and the tip end portions of the mounting metal 80 and the outer cylinder 90 of the outer metal fitting 70 (FIG. 1) reference).

  The insulating spacer 100 is composed of a cylindrical portion 100t having a substantially cylindrical shape, and an annular projecting portion 103 annularly protruding from the cylindrical portion 100t toward the radially outer side GDO (see FIGS. 5 and 6). Of the insulating spacer 100 (cylindrical portion 100t), the proximal end GK portion is an in-sensor exposed portion 100k exposed in the sensor internal space SIS (see FIGS. 1 and 2).

The cylindrical portion 100 t has a cylindrical spacer main body 101 made of alumina, and a layered heater portion 102 wound on the outer peripheral surface 101 g forming the cylindrical surface of the spacer main body 101. The layered heater portion 102 is wound around the outer peripheral surface 101 g of the spacer main body 101 so that both circumferential end portions of the layered heater portion 102 do not overlap, and has a single-layered cylindrical shape (cross-section C shape). In the part of the spacer main body 101 in the longitudinal direction GH along the axis AX, in the part closer to the distal end side GS, a thick thick portion 101f and a thin distal end thin portion 101s located on the distal end side GS than this are included. Have.
The annular projecting portion 103 is airtightly fitted on the layered heater portion 102 and protrudes toward the radially outer side GDO of the insulating spacer 100.

  As shown in FIG. 7, the layered heater section 102 includes a layered spacer heater 105, a base insulating layer 108 made of alumina located on the inner side, and a cover insulating layer located on the outer side of the spacer heater 105 made of alumina. And 109. The spacer heater 105 (see FIG. 7) includes a layered heating resistor 106 made of tungsten and a heater lead portion 107. Heater lead portion 107 penetrates lead body portion 107 p extending from both ends of heat generating resistor 106, terminal pad 107 m exposed on the surface of layered heater portion 102, and cover insulating layer 109 to lead body portion 107 p and terminal pad And a via conductor 107v electrically connected to 107m.

  Among these, the heating resistor 106 has a meander shape (zigzag shape) and has a form extending in the circumferential direction CD of the insulating spacer 100. Of the heating resistor 106, one end 106p located on the one side CD1 and the other end 106q located on the other side CD2 are wound around the spacer main body 101 as shown in FIG. It is disposed to face and be close to the circumferential direction CD. By causing the heat generating resistive element 106 of the spacer heater 105 to generate heat, the heat of the heat generating resistive element 106 can be transmitted to the in-sensor exposed portion 100k to heat the in-sensor exposed portion 100k.

  The heating resistor 106 of the spacer heater 105 is covered with the cover insulating layer 109 and embedded in the inside of the insulating spacer 100. For this reason, condensation water (water droplets produced by condensation) adheres (is deposited) on the heating resistor 106, so that it is not possible to properly execute energization to the spacer heater 105, or deterioration of the heating resistor 106 is suppressed. it can. Therefore, even when the particulate sensor 10 is used for a long time, the heating performance by the spacer heater 105 can be maintained well.

  The annular projecting portion 103 is an annular ring made of alumina, and a ceramic ring 103c externally fitted to the cylindrical portion 100t (specifically, the layered heater portion 102 provided on the outer periphery of the spacer main body 101), and this is a layered heater portion It is comprised by the glass seal part 103g which consists of glass airtightly fixed to 102. FIG. As shown in FIG. 1, the annular projection 103 is directed toward the tip side GS via the wire packing 87, the pressing sleeve 110, and the powder filling body 115 by caulking the crimped portion 80 kk of the mounting bracket 80. And is pressed against the stepped portion 83 of the mounting bracket 80. Thus, the insulating spacer 100 can be easily and airtightly fixed to the mounting bracket 80 by providing the annular projecting portion 103 on the insulating spacer 100.

  The insulating spacer 100 is formed as follows. Specifically, the unfired layered heater portion 102 including the heating resistor 106 and the lead main body portion 407 p formed by pattern printing is wound around the outer periphery of the calcined spacer main body 101 and is fired. Thereafter, the ceramic ring 103c is externally fitted, and the ceramic ring 103c is airtightly fixed with glass to provide a glass seal portion 103g. Thus, the insulating spacer 100 is formed.

  As shown in FIG. 2, the two heater lead portions 107 of the layered heater portion 102 of the insulating spacer 100 are connected to the heater lead wires 172 and 178 which are core wires of the single core electric wires 171 and 177 respectively. Connected through. Specifically, the tip portions of the heater lead wire 172 of the electric wire 171 and the heater lead wire 178 of the electric wire 177 are held and conducted to the connection terminals 181 and 182 brazed to the terminal pads 107m and 107m, respectively.

  Next, the ceramic element 120 will be described. The ceramic element 120 has a plate-like insulating ceramic base 121 made of alumina extending in the longitudinal direction GH (see FIGS. 8 and 9). The discharge electrode body 130, the auxiliary electrode body 140, and the heater 150 for the element are embedded in the ceramic base 121, and these are integrally sintered with the ceramic base 121.

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

  The discharge electrode body 130 has a form extending in the longitudinal direction GH, and a needle-like needle-like electrode portion 131 located on the distal side GS, a discharge potential pad 135 located on the proximal side GK, and the like And a lead portion 133 connecting the two. The needle-like electrode portion 131 is made of a platinum wire. On the other hand, the lead portion 133 and the discharge potential pad 135 are made of pattern printed tungsten. Of the discharge electrode body 130, the base end side portion 131k of the needle-like electrode portion 131 and the whole of the lead portion 133 are embedded in the ceramic base 121. On the other hand, the tip side portion 131s of the needle-like electrode portion 131 protrudes from the ceramic base 121 at the tip side GS of the ceramic base 121 with respect to the ceramic layer 122. Further, the discharge potential pad 135 is exposed on the proximal side GK of the ceramic base 121 relative to the ceramic layer 122. As described above, the discharge potential terminal 46 contacts the discharge potential pad 135 in the insertion hole 44 c of the first separator 44.

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

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

Next, the electric wires 161, 163, 171, 173, 175, and 177 will be described (see FIGS. 1 and 3). Of these six wires, two wires 161 and 163 are triple coaxial cables (triaxial cables), and the remaining four wires 171, 173, 175 and 177 are small diameter single core insulated wires. It is.
Among them, the electric wire 161 has a discharge potential lead wire 162 as a core wire (center conductor), and the discharge potential lead wire 162 is a discharge potential terminal 46 in the first insertion hole 45 c of the second separator 45 as described above. Connected to Further, the electric wire 163 has an auxiliary potential lead wire 164 as a core wire (central conductor), and the auxiliary potential lead wire 164 is connected to the auxiliary potential terminal 47 in the second insertion hole 45 d of the second separator 45. . Further, among the coaxial double outer conductors of the electric wires 161 and 163, the inner inner outer conductors 161g1 and 163g1 are connected to the inner cylinder connection fitting 50 of the inner fitting 20, and are set to the first potential PV1. . On the other hand, the outer outer conductors 161g2 and 163g2 on the outer side are connected to the outer cylinder connection fitting 95 which is conducted to the outer fitting 70, and are set to the ground potential PVE.

  Moreover, the electric wire 171 has a heater lead wire 172 as a core wire. Moreover, the electric wire 177 has a heater lead wire 178 as a core wire. As described above, the heater lead wires 172 and 178 are, through the connection terminals 181 and 182, the two heater lead portions 107 of the layered heater portion 102 of the insulating spacer 100 (specifically, the terminal pads 107m and 107m) It is connected to the. Moreover, the electric wire 173 has the 2-1st heater lead wire 174 as a core wire. The second-first heater lead wire 174 is connected to the second-first heater terminal 48 in the second insertion hole 45 d of the second separator 45. Moreover, the electric wire 175 has a 2nd-2 heater lead wire 176 as a core wire. The second 2-2 heater lead wire 176 is connected to the second 2-2 heater terminal 49 in the second insertion hole 45 d of the second separator 45.

  Next, the circuit unit 200 will be described. The circuit unit 200 is connected to the electric wires 161, 163, 171, 173, 175, and 177 of the particle sensor 10 as shown in FIG. 4 and 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.

Among these, the ion source power supply circuit 210 has a first output end 211 which is a first potential PV1 and a second output end 212 which is a second potential PV2. The second potential PV2 is a positive high potential with respect to the first potential PV1.
The auxiliary electrode power supply circuit 240 has an auxiliary first output end 241 set to the first potential PV1 and an auxiliary second output end 242 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 measurement control circuit 220 includes a signal current detection circuit 230, a first heater heating circuit 223, a second heater heating circuit 225, and a microprocessor 221. Among these, the signal current detection circuit 230 has a first input end 231 set to the first potential PV1 and a second input end 232. The signal current detection circuit 230 detects a signal current Is flowing between the first input end 231 and the second input end 232. The first potential PV1 is set higher than the ground potential PVE by the offset voltage V _offset (specifically, 0.5 V). Therefore, the second input terminal 232 is set to a potential higher than the ground potential PVE by the offset voltage V _offset (specifically, 0.5 V).

  The first heater heating circuit 223 further includes a 1-1 heater energization end 223 a connected to the heater lead wire 172 of the electric wire 171 and a 1-2 heater energization end 223 b set to the ground potential PVE. The first heater heating circuit 223 energizes the spacer heater 105 of the insulating spacer 100 by PWM control to cause the heating resistor 106 of the spacer heater 105 to generate heat.

  Further, the second heater heating circuit 225 is connected to a 2-1 heater conductive end 225 a connected to the 2-1 heater lead wire 174 of the electric wire 173 and to a 2-2 heater lead wire 176 of the electric wire 175. And a second 2-2 heater conductive end 225 b set to the ground potential PVE. The second heater heating circuit 225 energizes the element heater 150 of the ceramic element 120 by PWM control to cause the heating resistor 151 of the element heater 150 to generate heat.

  In the circuit unit 200, the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 are surrounded by the inner circuit case 250 which is set to the first potential PV1. Further, the inner circuit case 250 accommodates and surrounds the secondary side iron core 271b of the insulating transformer 270, and conducts to the inner outer conductors 161g1 and 163g1 of the electric wires 161 and 163 which are set to the first potential PV1. There is. In the insulation transformer 270, the iron core 271 is separated into a primary side iron core 271a wound with the primary side coil 272 and a secondary side iron core 271b wound with the power supply circuit side coil 273 and the auxiliary electrode power supply side coil 274. Is configured. Among these, the primary side iron core 271a conducts to the ground potential PVE, and the secondary side iron core 271b conducts to the first electric potential PV1.

  Furthermore, 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 which is set to the ground potential PVE. Further, the outer circuit case 260 accommodates and surrounds the primary side iron core 271a of the insulating transformer 270, and is electrically connected to the outer external conductors 161g2 and 163g2 of the electric wires 161 and 163 which are set to the ground potential PVE.

  The measurement control circuit 220 incorporates a regulator power supply PS. The regulator power supply PS is driven by the 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 via the isolation transformer 270. The measurement control circuit 220 has a microprocessor 221 and can communicate with the control unit ECU that controls the internal combustion engine via the communication line CC, and the measurement result of the signal current detection circuit 230 described above (signal current Signals such as the magnitude of Is) can be transmitted to the control unit ECU.

  Next, the electrical function and operation of the particle detection system 1 will be described. The discharge electrode body 130 of the ceramic element 120 is connected and conducted to the second output end 212 of the ion source power supply circuit 210 through the discharge potential lead wire 162 of the electric wire 161 and is set to the second potential PV2 (see FIG. 4, FIGS. 8 and 9). On the other hand, the auxiliary electrode body 140 of the ceramic element 120 is connected and conducted to the auxiliary second output end 242 of the auxiliary electrode power circuit 240 through the auxiliary potential lead wire 164 of the electric wire 163, and is made the auxiliary electrode potential PV3. Ru. Furthermore, the inner fitting 20 is connected and conducted to the inner circuit case 250 or the like through the inner outer conductors 161g1 and 163g1 of the electric wires 161 and 163, and is set to the first potential PV1 (FIG. 1, FIG. 3, FIG. 4). In addition, the outer fitting 70 is connected and conducted to the outer circuit case 260 or the like via the outer outer conductors 161g2 and 163g2 of the electric wires 161 and 163, and is set to the ground potential PVE.

  Here, in the needle electrode portion 131 of the discharge electrode body 130, the ion source power supply circuit 210 of the circuit portion 200, the discharge potential lead wire 162 of the electric wire 161, the discharge potential terminal 46, and the discharge potential pad 135 A second potential PV2 of a voltage (for example, 1 to 2 kV) is applied. Then, an air discharge, specifically, a corona discharge, is generated between the needle-like tip 131ss of the needle-like electrode 131 and the inner protector 60 set to the first potential PV1, and the needle-like tip 131ss The ion CP is generated in the surroundings (see FIG. 10).

  As described above, the exhaust gas EG is introduced into the inner protector 60 by the action of the gas intake pipe 25, and in the vicinity of the ceramic element 120, the air flow of the intake gas EGI from the proximal end GK toward the distal end GS It is happening. Therefore, the generated ions CP adhere to the particulates S in the intake gas EGI. Thereby, the particulates S become charged particulates SC charged positively, and flow toward the gas discharge port 60e together with the intake gas EGI, and are discharged to the exhaust pipe EP (see FIG. 10).

  On the other hand, in the auxiliary electrode portion 141 of the auxiliary electrode body 140, a predetermined potential (the auxiliary potential power lead wire 164 of the electric wire 163, the auxiliary potential terminal 47, and the auxiliary potential pad 147) For example, an auxiliary electrode potential PV3 of 100 to 200 V (positive direct current potential) is applied. As a result, among the generated ions CP, the floating ions CPF that did not adhere to the particulates S are given a repulsive force directed from the auxiliary electrode portion 141 toward the radially outer inner protector 60 (collection electrode). And floating ion CPF is made to adhere to each part of a collection pole (inner protector 60), and collection is assisted (refer to Drawing 10). Thus, the floating ion CPF can be reliably collected, and even the floating ion CPF can be prevented from being discharged from the gas outlet 60e.

  Then, in the particle detection system 1, the signal current detection circuit 230 detects a signal (signal current Is) corresponding to the charge amount of the discharge ion CPH attached to the charged particle SC discharged from the gas discharge port 60e. . Thereby, the amount (concentration) of the particulates S contained in the exhaust gas EG can be detected. As described above, in the present embodiment, the ion CP generated by the air discharge is made to adhere to the particulates S contained in the exhaust gas EG taken into the inside of the gas intake pipe 25 to generate the charged particulates SC charged. The amount of particulates S in the exhaust gas EG is detected between the first potential PV1 and the ground potential PVE using the signal current Is flowing according to the amount of the charged particulates SC.

  Furthermore, the particulate sensor 10 has a heater 150 for the element on the ceramic element 120. The 2-1st heater pad 156 of the heater 150 for the element is connected to the 2nd heater heating circuit 225 of the circuit section 200 via the 2-1th heater terminal 48 and the 2-1st heater lead wire 174 of the electric wire 173. 2-1 Conduction to the heater conduction end 225a. Further, the second 2-2 heater pad 158 of the element heater 150 is connected to the second 2-2 heater heater circuit 225 through the second 2-2 heater terminal 49 and the second 2-2 heater lead wire 176 of the electric wire 175. Conduction is made to the heater conduction end 225b.

  For this reason, when a predetermined heater energization voltage is applied between the 2-1 heater pad 156 and the 2-2 heater pad 158 from the second heater heating circuit 225, the heating resistor 151 of the element heater 150 is energized. Due to heat. As a result, the ceramic element 120 can be heated to remove foreign matter (water droplets, wrinkles, etc.) adhering to the ceramic element 120, so that the insulation of the ceramic element 120 can be recovered or maintained.

  By the way, as described above, the insulating spacer 100 of the present embodiment has the in-sensor exposed portion 100k exposed in the sensor internal space SIS. For this reason, in the particulate sensor 10 of the present embodiment, the following may occur. Specifically, for example, during operation of the engine (internal combustion engine), the particulate sensor 10 is heated by the high-temperature exhaust gas EG to a high temperature. The exhaust gas EG contains a large amount of water (water vapor), and this water (water vapor) may leak into the sensor internal space SIS during operation of the internal combustion engine. On the other hand, when the operation of the internal combustion engine is stopped, the particulate sensor 10 is cooled by the outside air. For this reason, for example, when the outside air temperature is low, dew condensation may occur on the surface of the in-sensor exposed portion 100k of the insulating spacer 100 after the operation of the internal combustion engine is stopped.

  When water (water generated by condensation) adheres to the surface of the sensor exposed portion 100k of the insulating spacer 100, the insulation of the surface of the sensor exposed portion 100k is reduced. As a result, the insulation between the inner fitting 20, which is the first potential PV1, and the outer fitting 70, which is the ground potential, is reduced. In such a state, when the particulate matter sensor 10 is driven to perform particulate matter detection, there is a possibility that the amount of the particulate matter S in the exhaust gas EG can not be appropriately detected.

  On the other hand, in the particulate sensor 10 of the present embodiment, the insulating spacer 100 has a spacer heater 105. One terminal pad 107 m of the spacer heater 105 is connected to the first heater conduction end 223 a of the first heater conduction circuit 223 via the connection terminal 181 and the heater lead wire 172 of the electric wire 171. The other terminal pad 107m of the spacer heater 105 is connected to the 1-2nd heater conductive end 223b of the first heater conductive circuit 223 through the connection terminal 182 and the heater lead 178 of the electric wire 177. Thus, the first heater energizing circuit 223 can energize the spacer heater 105 (heat generating resistor 106).

  Therefore, when the spacer heater 105 is energized by the first heater energizing circuit 223, the heating resistor 106 of the spacer heater 105 generates heat. Thereby, the sensor in-sensor exposed portion 100k of the insulating spacer 100 is heated to remove (evaporate) dew condensation water (water droplets generated by condensation) adhering to the surface of the in-sensor exposed portion 100k of the insulating spacer 100. Can. As a result, the insulation between the inner fitting 20, which is the first potential PV1, and the outer fitting 70, which is the ground potential PVE, can be restored.

In the particle detection system 1 of the present embodiment, it is checked whether the degree of insulation between the inner fitting 20 (first potential PV1) and the outer fitting 70 (ground potential PVE) is within the allowable range. . Specifically, as described above, an offset voltage V _offset (specifically, 0.5 V) is applied between the inner fitting 20 (first potential PV1) and the outer fitting 70 (ground potential PVE). Ru. Therefore, depending on the degree of insulation between the inner fitting 20 and the outer fitting 70, a leakage current Im flowing between the inner fitting 20 and the outer fitting 70 is generated. The leakage current Im is detected by the signal current detection circuit 230. The microprocessor 221 determines whether the magnitude of the leakage current Im detected by the signal current detection circuit 230 is within an allowable range (specifically, whether or not it is equal to or less than a preset reference value Ims (threshold)). To determine In the present embodiment, the “degree of insulation” is indicated by the magnitude of the leakage current Im.

  Note that the allowable range of the degree of insulation between the inner fitting 20 and the outer fitting 70, specifically, the reference value Ims (threshold value) of the leakage current Im is the particulate S in the exhaust gas EG by the particulate detection system 1. The amount of insulation can be properly detected in the range of the degree of insulation. When water droplets (condensed water) generated by condensation are attached to the surface of the exposed portion 100k in the sensor of the insulating spacer 100, the degree of insulation between the inner fitting 20 and the outer fitting 70 is not within the allowable range Specifically, it can be determined that the leakage current Im is larger than the reference value Ims (threshold).

  In the particulate matter detection system 1 of the present embodiment, as described above, the degree of insulation between the inner fitting 20 and the outer fitting 70 is not within the allowable range (specifically, the leakage current Im is higher than the reference value Ims) If it is determined that the value is large, the spacer heater 105 is energized by the first heater energization circuit 223 to cause the heating resistor 106 to generate heat. More specifically, the spacer heater 105 is operated by the first heater energizing circuit 223 for a predetermined first time t1 (for example, 5 minutes) in which water adhering to the surface of the in-sensor exposed portion 100k is expected to be removed. Energize the This energization is referred to as "first heater energization".

  By the first heater energization, the sensor in-sensor exposed portion 100k of the insulating spacer 100 is heated to remove condensation water (water droplets generated by condensation) adhering to the surface of the in-sensor exposed portion 100k of the insulating spacer 100 Can be evaporated). As a result, the insulation between the inner fitting 20, which is the first potential PV1, and the outer fitting 70, which is the ground potential PVE, can be restored.

  The first time t1 is set based on the result of the test performed in advance. Specifically, in a state where dew condensation water adheres to the surface of the exposed portion 100k in the sensor, the spacer heater 105 is energized by the first heater energizing circuit 223 to cause the heating resistor 106 to generate heat, and the exposed in the sensor A test was conducted to measure the elapsed time until condensation water adhering to the surface of the part 100k is completely removed (vaporized). In this embodiment, this elapsed time is set to the first time t1.

  Furthermore, in the particle detection system 1 of the present embodiment, the degree of insulation between the inner fitting 20 and the outer fitting 70 is within the allowable range (specifically, the leakage current Im is less than or equal to the reference value Ims) The particle sensor 10 is driven after it is determined that the first heater is energized (the process of energizing the spacer heater 105 by the first heater energizing circuit 223 for the first time t1).

  That is, if it is determined that the degree of insulation between the inner fitting 20 and the outer fitting 70 is within the allowable range (specifically, the leakage current Im is less than or equal to the reference value Ims), then fine particles The sensor 10 is driven to detect the amount of particulates S. Thereby, the amount of the particulates S in the exhaust gas EG can be appropriately detected.

  On the other hand, if it is determined that the degree of insulation between the inner fitting 20 and the outer fitting 70 is not within the allowable range (specifically, the leakage current Im is larger than the reference value Ims), the first heater energization ( After the end of the process of energizing the spacer heater 105 for the first time t1 by the first heater energizing circuit 223, the particle sensor 10 is driven to detect the amount of the particles S. Therefore, in the particle detection system 1 of the present embodiment, after the dew condensation water is removed from the surface of the in-sensor exposed portion 100k of the insulating spacer 100 by the first heater energization, the amount of particles S is detected. Thereby, the amount of the particulates S in the exhaust gas EG can be appropriately detected.

  In particular, in the particulate matter detection system 1 of the present embodiment, although the signal current Is becomes very small, as described above, after the leak current Im is determined to be equal to or less than the reference value Ims, or After the dew condensation water is removed from the surface of the inner exposed portion 100k, the amount of the particulates S is detected. Thereby, in the particulate matter detection system 1, the minute signal current Is can be appropriately detected without being affected by the leakage current Im, so the amount of the particulates S contained in the exhaust gas EG can be appropriately detected. .

Next, the flow of particulate detection in the present embodiment will be described. FIG. 11 is a flowchart showing the flow of particle detection according to the embodiment.
When a key switch (not shown) of the engine is turned on and engine operation is started, the signal current detection circuit 230 detects the first input end 231 and the second input end 231 in step S1 based on a command from the microprocessor 221. A leakage current Im flowing between the input terminal 232, that is, between the inner fitting 20 (first potential PV1) and the outer fitting 70 (ground potential PVE) is detected. Next, in step S2, the microprocessor 221 determines whether or not the magnitude of the leakage current Im detected by the signal current detection circuit 230 is within an allowable range (specifically, at or below a preset reference value Ims). To determine if it is

  If it is determined that the leakage current Im is equal to or less than the reference value Ims (YES), the process proceeds to step S3, and the microprocessor 221 drives the particle sensor 10. Specifically, as described above, the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 are driven to perform processing such as generation of ion CP by corona discharge.

  The microprocessor 221 and the signal current detection circuit 230 which perform the processes of steps S1 and S2 correspond to "insulation inspection means". Further, the microprocessor 221 performing the process of step S3, the ion source power supply circuit 210, and the auxiliary electrode power supply circuit 240 correspond to "sensor driving means".

  Next, in step S4, the amount of particulates S contained in the exhaust gas EG is detected. Specifically, as described above, the signal current detection circuit 230 detects a signal (signal current Is) corresponding to the charge amount of the discharge ion CPH. Thereby, the amount (concentration) of the particulates S contained in the exhaust gas EG can be detected.

On the other hand, if it is determined in step S2 that the leakage current Im is larger than the reference value Ims (NO), the process proceeds to step S5, and energization of the first heater is started. Specifically, based on an instruction from the microprocessor 221, the first heater energizing circuit 223 energizes the spacer heater 105 to cause the heating resistor 106 to generate heat.
Thereafter, in step S6, the microprocessor 221 determines whether or not the energization time from the first heater heating circuit 223 to the spacer heater 105 has reached a preset first time t1.

  In step S6, when it is determined that the current application time to the spacer heater 105 has reached the first time t1 (YES), the process proceeds to step S7, and the first heater heating circuit 223 based on a command from the microprocessor 221. The current supply to the spacer heater 105 is ended. If it is determined in step S6 that the energization time for the spacer heater 105 has not reached the first time t1 (NO), the determination process of step S6 is repeated until the energization time reaches the first time t1. By performing the processes of steps S5 to S7, the first heater energization is performed, and the condensed water adhering to the surface of the in-sensor exposed portion 100k of the insulating spacer 100 is removed (vaporized).

In step S7, when energization of the first heater is terminated by terminating energization of the spacer heater 105, the process proceeds to steps S3 and S4, and the above-described processing is performed to determine the amount of particulates S contained in the exhaust gas EG. Detect
The microprocessor 221 and the first heater heating circuit 223 that perform the processes of steps S5 to S6 correspond to "heater energization means".

  Thus, in the present embodiment, after the operation of the engine (internal combustion engine) is started, prior to the start of driving of the particulate sensor 10, the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is acceptable. It is checked whether it is within the range (specifically, whether the leakage current Im flowing between the inner fitting 20 and the outer fitting 70 is less than or equal to the reference value Ims).

When it is determined that the degree of insulation is within the allowable range (specifically, the leakage current Im is less than or equal to the reference value Ims), the particulate sensor 10 is driven to detect the amount of particulate S Do. On the other hand, if it is determined that the degree of insulation is not within the allowable range (specifically, the leakage current Im is larger than the reference value Ims), the first heater is energized to cause condensation from the surface of the exposed portion 100k in the sensor After removing the water, the particle sensor 10 is driven to detect the amount of the particles S.
Therefore, according to the particulate matter detection system 1 of the present embodiment, it is possible to appropriately detect the amount of the particulates S in the exhaust gas EG discharged from the engine after the operation of the engine (internal combustion engine) is started.

Although the present invention has been described above with reference to the embodiment, the present invention is not limited to the above-described embodiment, and it goes without saying that the present invention can be appropriately modified and applied without departing from the scope of the invention.
For example, although the heat generating resistor 106 made of tungsten is used in the embodiment, the constituent material of the heat generating resistor 106 is not limited thereto. Other metal materials such as platinum and molybdenum and conductive ceramic materials may be used.

In the embodiment, the flow described in the flowchart of FIG. 11 is illustrated as a specific particle detection flow, but the particle detection flow is not limited thereto. For example, in the embodiment, only one time in step S1. The leakage current Im is measured, and it is determined in step S2 whether or not the magnitude of the leakage current Im is within the allowable range (specifically, whether or not it is equal to or less than a preset reference value Ims). If the magnitude of the current Im is within the allowable range, the particle sensor 10 is driven in step S3. That is, based on the measurement result of the leak current Im only once, it was determined whether the degree of the insulation between the inner fitting 20 and the outer fitting 70 was within the allowable range.
However, even if leakage current Im is measured a plurality of times and whether the degree of insulation between inner metal fitting 20 and outer metal fitting 70 is within the allowable range is determined based on the measurement results of the plurality of times. good. For example, when the leakage current Im is measured three times, and in all three times, the magnitude of the leakage current Im is within the allowable range (specifically, it is the preset reference value Ims or less), the inner metal fitting 20 It is also possible to determine that the degree of insulation between the and the outer metal fitting 70 is within the allowable range, and drive the particulate sensor 10 in step S3. As described above, the reliability of the insulation determination can be enhanced by determining whether or not the insulation degree is within the allowable range based on the measurement results of the leak current Im a plurality of times, and thus, the particle detection is performed. Can increase the reliability of

1 particle detection system 10 particle sensor 20 inner metal fitting 25 gas intake pipe (inner metal fitting)
30 Main fitting (inner fitting)
40 inner cylinder (inner bracket)
50 inner cylinder connection bracket (inner bracket)
60 Inner protector (inner bracket)
60e Gas outlet 65 Outer protector (inner bracket)
65c Gas intake 70 Outer bracket 80 Mounting bracket (outer bracket)
90 Outer cylinder (outside bracket)
100 Insulating spacer 100 k Exposed portion in sensor 101 Spacer body 102 Layered heater portion 105 Heater for spacer (heater)
DESCRIPTION OF SYMBOLS 106 Heating resistor 120 Ceramic element 130 Discharge electrode body 140 Auxiliary electrode body 200 Circuit part 210 Ion source power supply circuit (sensor drive means)
221 Microprocessor (Insulation inspection means, sensor drive means, heater energization means)
223 1st heater heating circuit (heater energizing means)
230 Signal current detection circuit (insulation inspection means)
240 Auxiliary electrode power supply circuit (sensor drive means)
CP Ion EP Exhaust pipe (vent)
EG exhaust gas (gas to be measured)
EGI Intake gas Is Signal current PVE Ground potential PV1 First potential S Fine particles SC Charged particles SIS Sensor Internal space t1 First time

Claims (3)

In a particulate detection system for detecting particulates contained in a measurement gas flowing through a vent pipe,
A particulate sensor attached to the vent pipe at a ground potential;
And sensor driving means for driving the particulate sensor.
The particle sensor is
A cylindrical outer fitting that is attached to the vent pipe and brought to the ground potential;
An inner fitting that is at a first potential different from the ground potential and is radially surrounded by the outer fitting;
And a cylindrical insulating spacer interposed between the inner and outer metal fittings to electrically insulate them from each other.
The insulating spacer is
An in-sensor exposed portion exposed in a sensor internal space surrounded by the outer fitting at the outside of the vent pipe;
A heater for heating the exposed portion in the sensor;
The heater includes a heating resistor embedded inside the insulating spacer,
The particle detection system
Insulation inspection means for inspecting whether the degree of insulation between the inner and outer metal fittings is within an allowable range;
And heater energization means for energizing the heater to cause the heating resistor to generate heat.
The heater energizing means is
In the case where it is determined by the insulation inspection means that the degree of insulation is not within the allowable range, the heater may be configured to remove water adhering to the surface of the exposed portion in the sensor. The first heater is energized for 1 hour,
The sensor drive means is
A particle detection system for driving the particle sensor, after the insulation inspection means determines that the insulation degree is within the allowable range, or after the first heater is energized. The particle detection system according to claim 1, wherein
The particulate sensor generates an aerial discharge by being driven by the sensor driving means, and causes charged ions to adhere to the particulates contained in the gas to be measured by causing ions generated by the aerial discharge to be charged. A particle detection system for detecting the amount of particles in the gas to be measured using a signal current that flows between the first potential and the ground potential according to the amount of the charged particles. The particulate matter detection system according to claim 1 or 2, wherein
The vent pipe is an exhaust pipe of an internal combustion engine,
The measurement gas is an exhaust gas,
In the insulation inspection means, after the operation of the internal combustion engine is started, the degree of insulation between the inner metal fitting and the outer metal fitting is prior to the start of driving of the particulate sensor by the sensor driving means. A particle detection system for inspecting whether or not it is within the allowable range.

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