JP2017129501A - Fine particle detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine particle detection system capable of appropriately detecting the amount of fine particles contained in a measurement target gas.SOLUTION: A fine particle detection system includes insulation checking means for checking whether a degree of insulation between an inner metal fitting and outer metal fitting is within an acceptable range or not, and heater energizing means for energizing a heater to allow a heating resistor to generate heat. When the insulation checking means determines that the degree of insulation is not within the acceptable range, the heater energizing means performs a first heater energization process to energize the heater for a predetermined first time period t1, during which water adhered to a surface of an exposed portion of a sensor is expected to disappear. A sensor driving means is configured to drive the fine particle sensor after the insulation checking means determines that the degree of insulation is within the acceptable range, or after the first heater energization process is completed.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a particulate detection system, and more particularly to a particulate detection system that detects particulates contained in a gas to be measured flowing through a vent pipe.

  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 detection system that can directly detect the amount of particulates in the exhaust gas and detect the amount of particulates in the exhaust gas in order to detect a filter failure.

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

JP 2014-10099 A JP 2015-129712 A

  By the way, when the above-described insulating spacer has an in-sensor exposed portion exposed in the sensor internal space surrounded by the outer metal fitting outside the exhaust pipe, the following may occur. Specifically, for example, during operation of the internal combustion engine, the particulate sensor is heated by being heated by high-temperature exhaust gas. The exhaust gas contains a large amount of moisture (water vapor), and this moisture (water vapor) may leak (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. For this reason, for example, when the outside air temperature is low, after the operation of the internal combustion engine is stopped, condensation may occur on the surface of the exposed portion in the sensor of the insulating spacer.

  If water (water generated by condensation) adheres to the surface of the exposed part in the sensor of the insulating spacer, the insulation of the surface of the exposed part in the sensor is lowered. Thereby, the insulation between the inner metal fitting made into 1st electric potential and the outer metal fitting made into grounding potential falls. In such a state, if the particle sensor is driven by the sensor driving means to detect the particle, the amount of the particle in the exhaust gas (gas to be measured) may not be detected properly.

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

  One aspect of the present invention is a particulate detection system that detects particulates contained in a gas to be measured that flows through a vent pipe, and a particulate sensor that is attached to the vent pipe at a ground potential, and a sensor that drives the particulate sensor. Driving means, and the fine particle sensor is mounted on the vent pipe and has a cylindrical outer metal fitting that is set to the ground potential, and a first potential different from the ground potential, and the outer metal fitting is used in a radial direction. An inner metal fitting surrounded by a periphery, and a cylindrical insulating spacer that is interposed between the inner metal fitting and the outer metal fitting to electrically insulate both of the inner metal fitting and the outer metal fitting. And a heater that heats the exposed portion inside the sensor, and the heater is disposed inside the insulating spacer. Insulating inspection means for inspecting whether or not the degree of insulation between the inner metal fitting and the outer metal fitting is within a permissible range, including the embedded heating resistor, and the heater Heater energizing means for energizing the heating resistor to generate heat, and the heater energizing means, when the insulation test means determines that the degree of insulation is not within the allowable range, The heater is energized for a predetermined first time when water attached to the surface of the exposed portion in the sensor is expected to be removed, and the sensor driving means is operated by the insulating inspection means. The particulate detection system drives the particulate sensor after it is determined that the degree of insulation is within the allowable range, or after the first heater energization is completed.

  In the above-described particulate detection system, the insulating inspection means inspects whether or not the degree of insulation between the inner metal fitting and the outer metal fitting is within an allowable range. Specifically, for example, a predetermined voltage is applied between the inner metal fitting and the outer metal fitting, the magnitude of the leakage current flowing between the inner metal fitting and the outer metal fitting is measured, and the magnitude of the leakage current is within an allowable range. Or not (for example, whether or not it is equal to or less than a preset threshold value). In this case, the “degree of insulation” is indicated by the magnitude of the leakage current.

  In addition, the allowable range of the degree of insulation between the inner metal fitting and the outer metal fitting is set to a range of the degree of insulation that can appropriately detect the amount of fine particles in the gas to be measured by the fine particle detection system. . If water droplets generated by condensation (hereinafter also referred to as condensed water) adhere to the surface of the exposed part of the insulating spacer in the sensor, the degree of insulation between the inner and outer brackets is not within the allowable range. Can be determined.

  Furthermore, in the fine particle detection system described above, when the insulation test means determines that the degree of insulation is not within the allowable range, the heater energization means conducts the first heater energization. Specifically, the heater energizing unit energizes the heater for a predetermined first time (for example, 5 minutes) that is expected to remove water attached to the surface of the exposed portion in the sensor. Thereby, the dew condensation water adhering to the surface of the exposed part in the sensor can be removed (evaporated).

  Further, in the fine particle detection system described above, the sensor drive means drives the fine particle sensor after the insulation test means determines that the degree of insulation is within the allowable range or after the first heater energization is completed. To do.

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

  In the fine particle sensor described above, the heater includes a heating resistor embedded in the insulating spacer. That is, the heating resistor is disposed inside the insulating spacer. Thereby, it can prevent that dew condensation water adheres to a heating resistor. For this reason, it is possible to prevent the heater from being properly energized or the deterioration of the heating resistor due to the condensation water adhering to the heating resistor. Therefore, even when the fine particle sensor is used for a long period of time, the heating performance by the heater can be maintained well.

  Furthermore, in the above particulate detection system, the particulate sensor generates air discharge by being driven by the sensor driving means, and ions generated by the air discharge are included in the gas to be measured. The charged fine particles are generated by adhering to the fine particles, and the fine particles in the gas to be measured are generated using a signal current flowing according to the amount of the charged fine particles between the first potential and the ground potential. It is preferable to use a particulate detection system that detects the amount of the particles.

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

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

  Furthermore, in any one of the fine particle detection systems described above, the vent pipe is an exhaust pipe of an internal combustion engine, the gas to be measured is exhaust gas, and the insulation inspection unit is configured to operate the internal combustion engine. After being started, prior to the start of driving of the particle sensor by the sensor driving means, the particle for inspecting whether or not the degree of insulation between the inner metal fitting and the outer metal fitting is within the allowable range. A detection system should be used.

  According to the fine particle detection system described above, after the operation of the internal combustion engine is started, the amount of fine particles in the exhaust gas discharged from the internal combustion engine can be appropriately detected.

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

  Embodiments of the present invention will be described below 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. 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 particle sensor 10. FIG. 4 is a schematic diagram 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 of the particle sensor 10 (the electric wire 161 and the like) is illustrated.

  1, in the longitudinal direction GH along the axis AX of the particle sensor 10, the side (downward in FIG. 1) on which the gas intake pipe 25 is arranged is the tip side GS, and the wires 161, 163 on the opposite side, etc. The side (upward in FIG. 1) from which the is extended is defined as a base end side GK.

  The fine particle detection system 1 detects the amount of fine particles S (soot etc.) contained in exhaust gas (measured gas) EG flowing through an exhaust pipe (vent pipe) EP of an internal combustion engine (engine). The fine particle detection system 1 includes a fine 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 having a ground potential PVE (see FIG. 1). Specifically, a gas intake pipe 25 that forms the tip side portion of the inner metal fitting 20 in the particulate sensor 10 is disposed in the exhaust pipe EP through an attachment opening EPO provided in the exhaust pipe EP. Then, among the exhaust gas EG flowing through the exhaust pipe EP, ions CP are attached to the fine particles S in the intake gas EGI taken into the gas intake pipe 25 from the gas intake port 65c to form charged fine particles SC. Together with the input gas EGI, the gas is discharged from the gas discharge port 60e to the exhaust pipe EP (see FIG. 10).

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

  Among these, the inner metal fitting 20 is electrically connected to the inner circuit case 250 or the like having 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 metal fitting 20 includes a main metal fitting 30, an inner cylinder 40, an inner cylinder connecting metal fitting 50, and a gas intake pipe 25 (an inner protector 60 and an outer protector 65).

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

  Inside the metallic shell 30, a cylindrical ceramic holder 34 made of alumina and compressed with talc powder around the ceramic element 120 in order from the distal end GS to the proximal end GK. A filling layer 35 and a second powder filling layer 36 and a cylindrical ceramic sleeve 37 made of alumina are arranged. The ceramic holder 34 and the first powder filling layer 35 are located in the metal cup 33. Further, the caulking portion 30kk on the most proximal side GK of the metal shell 30 is caulked inward in the radial direction to press the ceramic sleeve 37 to the distal end GS via the caulking ring 38.

  The metal shell 30 has a male screw portion 30n between the flange portion 31 and the tip portion 30s. A spacer retaining ring 32 that engages an insulating spacer 100 described later via a wire packing 39 is screwed to the male screw portion 30n. As a result, the thick portion 101f of the spacer 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 are interposed via the insulating spacer 100 as will be described later. The ceramic element 120 and the like held thereby are fixed to the mounting bracket 80.

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

  Inside the inner cylinder 40, an insulating holder 43, a first separator 44, and a second separator 45 are arranged in order from the distal end side GS to the proximal end side GK. Of these, the insulating holder 43 is cylindrical and made of an insulator, and is in contact with the ceramic sleeve 37 from the base end side 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 side portion of the discharge potential terminal 46 is accommodated. In the insertion hole 44c, a discharge potential terminal 46 is in contact with a discharge potential pad 135 (see FIGS. 8 and 9) described later 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. A proximal end portion of the discharge potential terminal 46 accommodated in the first insertion hole 45c and a distal end portion of a discharge potential lead wire 162 to be described later are connected in the first insertion hole 45c.

  In addition, the element base end portion 120k of the ceramic element 120 is disposed in the second insertion hole 45d, and the auxiliary potential terminal 47, the 2-1 heater terminal 48, and the 2-2 heater terminal 49 are insulated from each other. It is housed in the state where it was done. In the second insertion hole 45d, the auxiliary potential terminal 47 contacts the auxiliary potential pad 147 of the ceramic element 120, and the 2-1 heater terminal 48 contacts the 2-1 heater pad 156 of the ceramic element 120. The 2-2 heater terminal 49 is in contact with the 2-2 heater pad 158 of the ceramic element 120 (see FIGS. 1, 2, 8, and 9).

  Furthermore, the distal end 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 disposed in the second insertion hole 45d. In the second insertion hole 45d, the auxiliary potential terminal 47 and the auxiliary potential lead wire 164 are connected, the 2-1 heater terminal 48 and the 2-1 heater lead wire 174 are connected, and the 2-2 heater terminal. 49 and the 2-2 heater lead wire 176 are connected.

  The inner cylinder connection fitting 50 is a member made of stainless steel and is fitted on the proximal end portion 40k of the inner cylinder 40 while surrounding the proximal end portion of the second separator 45, and the distal end portion 50s of the inner cylinder connection fitting 50 is Laser welding is performed on the base end portion 40 k of the inner cylinder 40. The four electric wires 161, 163, 173, and 175 except for the electric wires 171 and 177 are inserted into 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 to be described later are connected to the inner tube connection fitting 50.

  The gas intake pipe 25 includes an inner protector 60 and an outer protector 65. The inner protector 60 is a bottomed cylindrical and stainless steel member, and the outer protector 65 is a cylindrical and stainless steel member. The outer protector 65 is arranged around the inner protector 60 in the radial direction. The inner protector 60 and the outer protector 65 are fitted on the distal end portion 30s of the metal shell 30, and are laser-welded to the distal end portion 30s. The gas intake pipe 25 surrounds the tip side portion of the ceramic element 120 protruding from the metal shell 30 to the tip side GS from the outside in the radial direction, and protects the ceramic element 120 from water droplets and foreign matters, while the exhaust gas EG is ceramic. Guide around the element 120.

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

  Here, the 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 circulates in the exhaust pipe EP from left to right. When the exhaust gas EG passes around the outer protector 65 and the inner protector 60, the flow velocity increases outside the gas discharge port 60e of the inner protector 60, and a negative pressure is generated near the gas discharge port 60e due to the venturi effect. .

  Then, the intake gas EGI taken into the inner protector 60 by this negative pressure is discharged from the gas discharge port 60e to the exhaust pipe EP. At the same time, the 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. Then, the intake gas EGI in the inner protector 60 is discharged from the gas discharge port 60e. For this reason, in the inner protector 60, an air flow of the intake gas EGI that flows from the first inner introduction hole 60c on the base end side GK toward the gas discharge port 60e on the front end side GS is generated, as indicated by a broken line arrow.

  Next, the outer metal fitting 70 will be described. As shown in FIGS. 1 and 3, the outer metal fitting 70 is cylindrical and made of metal, surrounds the inner circumference of the inner metal fitting 20 in a state of being separated from the inner metal fitting 20, and is an exhaust pipe having a ground potential PVE. Attached to the EP is set to the ground potential PVE. The outer metal fitting 70 is composed of an attachment metal 80 and an outer cylinder 90.

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

  An insulating spacer 100 described later is disposed between the outer metal fitting 70 and the inner metal fitting 20, more specifically, between the mounting metal fitting 80 and the metal shell 30. The caulking portion 80kk on the most proximal side GK of the mounting bracket 80 is caulked to the radially inner GDI, and the annular protrusion of the insulating spacer 100 is interposed via the wire packing 87, the pressing sleeve 110, and the powder filler 115. The insulating spacer 100 is fixed to the mounting bracket 80 by pressing 103 to the tip side GS and press-contacting 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 fitted on the proximal end side portion 80k of the mounting bracket 80, and is laser welded to the proximal end side portion 80k. An outer cylinder connection fitting 95 is arranged inside the small diameter portion 91 located on the base end side GK in the outer cylinder 90, and a fluoro rubber grommet 97 is arranged on the base end side GK. Six electric wires 161, 163, 171, 173, 175, and 177, which will be described later, are inserted into the outer tube connecting fitting 95 and the grommet 97, respectively. Among these, the outer outer conductors 161g2 and 163g2 of the electric wires 161 and 163 of the triple coaxial cable described later are connected to the outer tube connection fitting 95, respectively. The outer cylinder connection fitting 95 is reduced in diameter in the radial direction 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.

  In the state where 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 defined as the sensor internal space. The SIS is used (see FIGS. 1 and 2).

  Next, the insulating spacer 100 will be described. As shown in FIGS. 5 and 6, the insulating spacer 100 has a cylindrical shape 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 metal fitting 20 and the outer metal fitting 70 to electrically insulate them. Specifically, it is arranged between the front end side portions of the metal shell 30 and the inner cylinder 40 of the inner metal fitting 20 and the front end side portions of the mounting metal fitting 80 and the outer cylinder 90 of the outer metal fitting 70 (FIG. 1). reference).

  The insulating spacer 100 includes a substantially cylindrical tubular portion 100t and an annular projecting portion 103 projecting annularly from the tubular portion 100t to the radially outer side GDO (see FIGS. 5 and 6). Of the insulating spacer 100 (cylindrical portion 100t), the base end side GK portion is an in-sensor exposed portion 100k exposed in the sensor internal space SIS (see FIGS. 1 and 2).

The cylindrical portion 100t includes a cylindrical spacer main body 101 made of alumina, and a layered heater portion 102 wound around an outer peripheral surface 101g forming a cylindrical surface of the spacer main body 101. The layered heater portion 102 is wound around the outer peripheral surface 101g of the spacer body 101 so that both ends in its circumferential direction do not overlap each other, and forms a single cylindrical shape (C-shaped cross section). In the spacer main body 101, a portion near the distal end GS in the longitudinal direction GH along the axis AX includes a thick portion 101f having a thicker thickness and a thin distal portion 101s located on the distal end GS than the thick portion 101s. Have.
The annular projecting portion 103 is airtightly fitted to the layered heater portion 102 and projects 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, an insulating base layer 108 made of alumina located inside thereof, and an insulating cover layer made of alumina located outside the spacer heater 105. 109. The spacer heater 105 (see FIG. 7) includes a layered heating resistor 106 made of tungsten and a heater lead 107. The heater lead portion 107 includes a lead main body portion 107p extending from both ends of the heating resistor 106, a terminal pad 107m exposed on the surface of the layered heater portion 102, a cover insulating layer 109 and the lead main body portion 107p and the terminal pad. The via conductor 107v is electrically connected to 107m.

  Among them, 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 one side CD1 and the other end 106q located on the other side CD2 are wound around the spacer body 101 as shown in FIG. Opposing and adjoining in the circumferential direction CD. By causing the heating resistor 106 of the spacer heater 105 to generate heat, the heat of the heating resistor 106 is transmitted to the exposed portion 100k in the sensor, and the exposed portion 100k in the sensor can be heated.

  The heating resistor 106 of the spacer heater 105 is covered with the insulating cover layer 109 and embedded in the insulating spacer 100. For this reason, it is possible to prevent the energization of the spacer heater 105 from being appropriately performed or the deterioration of the heating resistor 106 due to the adhesion (deposition) of condensed water (water droplets generated by condensation) to the heating resistor 106. it can. Therefore, even when the fine particle sensor 10 is used for a long period of time, the heating performance by the spacer heater 105 can be maintained satisfactorily.

  The annular projecting portion 103 is an annular shape made of alumina, and a ceramic ring 103c fitted on the cylindrical portion 100t (specifically, the layered heater portion 102 provided on the outer periphery of the spacer main body 101) and the layered heater portion. And a glass seal portion 103g made of glass that is hermetically fixed to 102. As shown in FIG. 1, the annular projecting portion 103 is directed toward the distal end GS via the wire packing 87, the pressing sleeve 110, and the powder filler 115 by crimping the crimping portion 80 kk of the mounting bracket 80. And pressed against the stepped portion 83 of the mounting bracket 80. As described above, the insulating spacer 100 can be easily and airtightly fixed to the mounting bracket 80 by providing the insulating spacer 100 with the annular protrusion 103.

  The insulating spacer 100 is formed as follows. Specifically, an unfired layered heater portion 102 including a heating resistor 106 and a lead main body portion 407p formed by pattern printing is wound around the outer periphery of the calcined spacer main body 101 and fired. Thereafter, the ceramic ring 103c is externally fitted to this, and this is hermetically fixed with glass to provide a glass seal portion 103g. Thereby, 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 heater lead wires 172 and 178, which are the core wires of the single-core electric wires 171 and 177, respectively. Connected through. Specifically, the connection terminals 181 and 182 brazed to the terminal pads 107m and 107m hold and conduct 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, 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). A discharge electrode body 130, an auxiliary electrode body 140, and an element heater 150 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 are interposed, respectively. Among these, the ceramic layer 122 and the insulating coating layer 125 are shorter than the ceramic layers 123 and 124 and the insulating coating layer 126 in the longitudinal direction GH on the distal end side GS and the proximal end side GK, respectively. The discharge electrode body 130 is disposed between the insulating coating layer 125 and the ceramic layer 123. The auxiliary electrode body 140 is disposed between the ceramic layer 123 and the insulating coating layer 126, and the element heater 150 is disposed between the insulating coating layer 126 and the ceramic layer 124.

  The discharge electrode body 130 has a form extending in the longitudinal direction GH, and has a needle-like needle electrode portion 131 located on the distal end side GS, a discharge potential pad 135 located on the proximal end side GK, and a gap therebetween. And a lead portion 133 connecting the two. The needle electrode part 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 131 k of the needle electrode portion 131 and the entire lead portion 133 are embedded in the ceramic base 121. On the other hand, the tip side portion 131 s of the needle electrode portion 131 protrudes from the ceramic base 121 on the tip side GS of the ceramic base 121 than the ceramic layer 122. Further, the discharge potential pad 135 is exposed in the base end side GK of the ceramic base 121 relative to the ceramic layer 122. The discharge potential pad 135 contacts the discharge potential terminal 46 in the insertion hole 44c of the first separator 44 as described above.

  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 includes a rectangular auxiliary electrode portion 141 located on the distal end side GS and a lead portion 143 connected to the auxiliary electrode portion 141 and extending to the proximal end side GK. The base end portion 143k of the lead portion 143 is connected to the conductive pattern 145 formed on one main surface 124a of the ceramic layer 124 through the through hole 126c of the insulating coating layer 126. Further, the conductive pattern 145 is connected to an auxiliary potential pad 147 formed on the other main surface 124 b of the ceramic layer 124 through a through-hole conductor 146 formed through the ceramic layer 124. The auxiliary potential pad 147 contacts the auxiliary potential terminal 47 in the second insertion hole 45d of the second separator 45 as described above.

  The element heater 150 is formed by pattern printing, and is entirely embedded in the ceramic substrate 121. The element heater 150 is located at the distal end GS and heats the ceramic element 120, and a pair of heater leads 152 and 153 connected to both ends of the heating resistor 151 and extending to the proximal end GK. Consists of. A base end portion 152k of one heater lead portion 152 is connected to a 2-1 heater pad 156 formed on the other main surface 124b of the ceramic layer 124 through a through-hole conductor 155 penetratingly formed in the ceramic layer 124. Connected. As described above, the 2-1 heater pad 48 is in contact with the 2-1 heater pad 156 in the second insertion hole 45d of the second separator 45. The base end portion 153k of the other heater lead portion 153 is a second-second heater pad formed on the other main surface 124b of the ceramic layer 124 via a through-hole conductor 157 penetratingly formed in the ceramic layer 124. 158. As described above, the 2-2 heater pad 49 contacts the 2-2 heater pad 158 in the second insertion hole 45d 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 these, 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 45c of the second separator 45 as described above. Connected to. The electric wire 163 has an auxiliary potential lead wire 164 as a core wire (center 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 these electric wires 161 and 163, the inner inner outer conductors 161g1 and 163g1 are connected to the inner cylinder connecting metal fitting 50 of the inner metal 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 an outer tube connection fitting 95 that is electrically connected 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. The electric wire 177 has a heater lead 178 as a core wire. As described above, the heater lead wires 172 and 178 are connected to the two heater lead portions 107 (specifically, the terminal pads 107m and 107m) of the layered heater portion 102 of the insulating spacer 100 through the connection terminals 181 and 182, respectively. It is connected to the. Moreover, the electric wire 173 has the 2-1 heater lead wire 174 as a core wire. The 2-1 heater lead wire 174 is connected to the 2-1 heater terminal 48 in the second insertion hole 45 d of the second separator 45. Moreover, the electric wire 175 has the 2-2 heater lead wire 176 as a core wire. The 2-2 heater lead wire 176 is connected to the 2-2 heater terminal 49 in the second insertion hole 45d of the second separator 45.

  Next, the circuit unit 200 will be described. As shown in FIG. 4, the circuit unit 200 is connected to the electric wires 161, 163, 171, 173, 175, and 177 of the particle sensor 10, 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 includes a first output terminal 211 having a first potential PV1 and a second output terminal 212 having a second potential PV2. The second potential PV2 is set to a positive high potential with respect to the first potential PV1.
The auxiliary electrode power circuit 240 has an auxiliary first output terminal 241 that is set to the first potential PV1 and an auxiliary second output terminal 242 that is set to the auxiliary electrode potential PV3. The auxiliary electrode potential PV3 is a positive DC high potential with respect to the first potential PV1, but is lower than the peak potential of the second potential PV2.

The measurement control circuit 220 includes a signal current detection circuit 230, a first heater heat generation circuit 223, a second heater heat generation circuit 225, and a microprocessor 221. Among these, the signal current detection circuit 230 includes a first input terminal 231 that is set to the first potential PV1 and a second input terminal 232. The signal current detection circuit 230 detects the signal current Is flowing between the first input terminal 231 and the second input terminal 232. The first potential PV1 is higher than the ground potential PVE by an offset voltage _Voffset (specifically, 0.5V). Accordingly, the second input terminal 232 is set to a potential that is higher than the ground potential PVE by an offset voltage V _offset (specifically, 0.5 V).

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

  The second heater heating circuit 225 is connected to the 2-1 heater conduction end 225a connected to the 2-1 heater lead wire 174 of the electric wire 173 and the 2-2 heater lead wire 176 of the electric wire 175. A 2-2 heater energization end 225b having a ground potential PVE. The second heater heat generating circuit 225 energizes the element heater 150 of the ceramic element 120 by PWM control, and causes the heat generating 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 an inner circuit case 250 having a first potential PV1. The inner circuit case 250 encloses and surrounds the secondary iron core 271b of the insulating transformer 270 and is electrically connected to the inner outer conductors 161g1 and 163g1 of the electric wires 161 and 163, which are set to the first potential PV1. Yes. The insulation transformer 270 has an iron core 271 separated into a primary iron core 271a wound around the primary coil 272 and a secondary iron core 271b wound around the power circuit coil 273 and the auxiliary electrode power supply coil 274. Configured. Among these, the primary side iron core 271a is conducted to the ground potential PVE, and the secondary side iron core 271b is conducted to the first potential PV1.

  Further, the ion source power supply circuit 210, the auxiliary electrode power supply circuit 240, the inner circuit case 250, and the measurement control circuit 220 are surrounded by an outer circuit case 260 having a ground potential PVE. The outer circuit case 260 houses and surrounds the primary iron core 271a of the insulating transformer 270, and is electrically connected to the outer outer conductors 161g2 and 163g2 of the electric wires 161 and 163, which are set to the ground potential PVE.

  The measurement control circuit 220 includes a regulator power source PS. The regulator power supply PS is driven by an external battery BT through the power supply wiring BC. A part of the power input to the measurement control circuit 220 through the regulator power supply PS is distributed to the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 through the isolation transformer 270. The measurement control circuit 220 includes a microprocessor 221 and can communicate with a control unit ECU that controls the internal combustion engine via a communication line CC. The measurement result (signal current) of the signal current detection circuit 230 described above is used. A signal such as (Is magnitude) can be transmitted to the control unit ECU.

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

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

  As described above, the exhaust gas EG is taken into the inner protector 60 by the action of the gas intake pipe 25, and in the vicinity of the ceramic element 120, the flow of the intake gas EGI from the proximal end GK toward the distal end GS is generated. Has occurred. Therefore, the generated ions CP adhere to the fine particles S in the intake gas EGI. As a result, the fine particles S become positively charged charged particles SC, 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, the auxiliary electrode portion 141 of the auxiliary electrode body 140 has a predetermined potential (from the auxiliary electrode power circuit 240 of the circuit portion 200 through the auxiliary potential lead wire 164 of the electric wire 163, the auxiliary potential terminal 47, and the auxiliary potential pad 147). For example, the auxiliary electrode potential PV3 set to 100 to 200 V (positive DC potential) is applied. As a result, repulsive force directed from the auxiliary electrode portion 141 toward the radially inner protector 60 (collecting electrode) is applied to the floating ions CPF that have not adhered to the fine particles S among the generated ions CP. Then, floating ions CPF are attached to each part of the collection electrode (inner protector 60) to assist the collection (see FIG. 10). Thus, the floating ions CPF can be reliably collected, and even the floating ions CPF are prevented from being discharged from the gas outlet 60e.

  In the particulate detection system 1, the signal current detection circuit 230 detects a signal (signal current Is) corresponding to the charge amount of the discharged ions CPH attached to the charged particulate SC discharged from the gas discharge port 60 e. . Thereby, the amount (concentration) of the fine particles S contained in the exhaust gas EG can be detected. As described above, in the present embodiment, the charged CP is generated by attaching the ions CP generated by the air discharge to the fine particles S contained in the exhaust gas EG taken into the gas intake pipe 25. Then, the amount of fine particles S in the exhaust gas EG is detected using a signal current Is that flows according to the amount of charged fine particles SC between the first potential PV1 and the ground potential PVE.

  Further, the fine particle sensor 10 includes an element heater 150 in the ceramic element 120. The 2-1 heater pad 156 of the element heater 150 is connected to the second heater heating circuit 225 of the circuit section 200 via the 2-1 heater terminal 48 and the 2-1 heater lead 174 of the electric wire 173. 2-1. Conduction to the heater energization end 225a. Further, the 2-2 heater pad 158 of the element heater 150 is connected to the 2-2 heater pad 49 of the second heater heating circuit 225 via the 2-2 heater terminal 49 and the 2-2 heater lead 176 of the electric wire 175. It is electrically connected to the heater energization end 225b.

  Therefore, when a predetermined heater energization voltage is applied between the second 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. Generates heat. Thereby, the ceramic element 120 can be heated to remove foreign matters (water droplets, wrinkles, etc.) adhering to the ceramic element 120, so that the insulation of the ceramic element 120 can be recovered or maintained.

  Incidentally, 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 fine particle 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 to a high temperature by being heated by the high-temperature exhaust gas EG. The exhaust gas EG contains a large amount of moisture (water vapor), and this moisture (water vapor) may leak (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 in-sensor exposed portion 100k of the insulating spacer 100, the insulating property of the surface of the in-sensor exposed portion 100k decreases. Thereby, the insulation between the inner metal fitting 20 set to the first potential PV1 and the outer metal fitting 70 set to the ground potential is lowered. If the particulate sensor 10 is driven and particulate detection is performed in such a state, the amount of the particulate S in the exhaust gas EG may not be detected appropriately.

  On the other hand, the particle sensor 10 of the present embodiment has a spacer heater 105 in the insulating spacer 100. One terminal pad 107 m of the spacer heater 105 is connected to the first heater energization end 223 a of the first heater energization circuit 223 via the connection terminal 181 and the heater lead wire 172 of the electric wire 171. The other terminal pad 107 m of the spacer heater 105 is connected to the first-second heater energization end 223 b of the first heater energization circuit 223 via the connection terminal 182 and the heater lead wire 178 of the electric wire 177. As a result, the first heater energization circuit 223 can energize the spacer heater 105 (heating resistor 106).

  For this reason, when the first heater energization circuit 223 energizes the spacer heater 105, the heating resistor 106 of the spacer heater 105 generates heat. Thereby, the exposed portion 100k in the sensor of the insulating spacer 100 is heated to remove (evaporate) condensed water (water droplets generated by the condensation) adhering to the surface of the exposed portion 100k in the sensor of the insulating spacer 100. Can do. Thereby, the insulation between the inner metal fitting 20 set to the first potential PV1 and the outer metal fitting 70 set to the ground potential PVE can be recovered.

In the fine particle detection system 1 according to the present embodiment, it is inspected whether the degree of insulation between the inner metal fitting 20 (first potential PV1) and the outer metal fitting 70 (ground potential PVE) is within an allowable range. . Specifically, as described above, the offset voltage V _offset (specifically, 0.5 V) is applied between the inner metal fitting 20 (first potential PV1) and the outer metal fitting 70 (ground potential PVE). The For this reason, a leakage current Im flowing between the inner metal fitting 20 and the outer metal fitting 70 is generated according to the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70. This leakage current Im is detected by the signal current detection circuit 230. 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, whether it is equal to or less than a preset reference value Ims (threshold)). )). In the present embodiment, the “degree of insulation” is indicated by the magnitude of the leakage current Im.

  The allowable range of the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70, specifically, the reference value Ims (threshold value) of the leakage current Im is determined by the fine particle detection system 1 by the fine particles S in the exhaust gas EG. It is set in the range of the degree of insulation which can detect the quantity of this appropriately. When water droplets (condensation 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 metal fitting 20 and the outer metal fitting 70 is not within an allowable range. Specifically, it can be determined that the leakage current Im is larger than the reference value Ims (threshold value).

  In the particulate detection system 1 of the present embodiment, as described above, the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is not within an allowable range (specifically, the leakage current Im is lower than the reference value Ims. If it is determined that it is large, the first heater energization circuit 223 energizes the spacer heater 105 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) that is expected to remove water attached to the surface of the exposed portion 100k in the sensor. Energize to. This energization is referred to as “first heater energization”.

  The first heater energization heats the exposed portion 100k of the insulating spacer 100 in the sensor to remove condensed water (water droplets generated by condensation) adhering to the surface of the exposed portion 100k of the insulating spacer 100 in the sensor ( Evaporate). Thereby, the insulation between the inner metal fitting 20 set to the first potential PV1 and the outer metal fitting 70 set to the ground potential PVE can be recovered.

  The first time t1 is set based on the results of tests performed in advance. Specifically, in a state where condensed water is attached to the surface of the exposed portion 100k in the sensor, the first heater energizing circuit 223 energizes the spacer heater 105 to cause the heating resistor 106 to generate heat, and the in-sensor exposure is started from the start of energization. The test which measures the elapsed time until the condensed water adhering to the surface of the part 100k is completely removed (evaporates) was done. In the present embodiment, this elapsed time is set to the first time t1.

  Furthermore, in the particulate detection system 1 of the present embodiment, the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is within an allowable range (specifically, the leakage current Im is equal to or less than the reference value Ims). Or after the first heater energization (the process of energizing the spacer heater 105 for the first time t1 by the first heater energization circuit 223) is completed.

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

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

  In particular, in the particulate detection system 1 of the present embodiment, the signal current Is is very small, but as described above, after the leakage current Im is determined to be equal to or less than the reference value Ims, or the first heater is energized. After the condensed water is removed from the surface of the inner exposed portion 100k, the amount of the fine particles S is detected. Thereby, in the particulate detection system 1, since the minute signal current Is can be appropriately detected without being affected by the leakage current Im, the amount of the particulate S contained in the exhaust gas EG can be appropriately detected. .

Next, the flow of particulate detection according to the present embodiment will be described. FIG. 11 is a flowchart showing a flow of particle detection according to the embodiment.
When an engine key switch (not shown) is turned on and engine operation is started, the signal current detection circuit 230 is connected to the first input terminal 231 and the second input based on a command from the microprocessor 221 in step S1. A leakage current Im flowing between the input end 232, that is, between the inner metal fitting 20 (first potential PV1) and the outer metal 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, not more than a preset reference value Ims). Whether or not there 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 particulate 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 processes such as generating ions CP by corona discharge.

  Note that the microprocessor 221 and the signal current detection circuit 230 that perform the processes of steps S1 and S2 correspond to “insulation inspection means”. Further, the microprocessor 221, the ion source power supply circuit 210, and the auxiliary electrode power supply circuit 240 that perform the processing of step S3 correspond to “sensor driving means”.

  Next, the process proceeds to step S4, and the amount of fine particles 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 discharged ions CPH. Thereby, the amount (concentration) of the fine particles 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 greater than the reference value Ims (NO), the process proceeds to step S5 and the first heater energization is started. Specifically, the first heater energizing circuit 223 energizes the spacer heater 105 based on a command from the microprocessor 221 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.

  If it is determined in step S6 that the energization time of the spacer heater 105 has reached the first time t1 (YES), the process proceeds to step S7, and the first heater heat generating circuit 223 is based on a command from the microprocessor 221. Terminates energization of the spacer heater 105. 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 in step S6 is repeated until the energization time reaches the first time t1. By performing the processing 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 (evaporates).

In step S7, when the first heater energization is completed by ending energization to the spacer heater 105, the process proceeds to steps S3 and S4, and the above-described processing is performed to reduce the amount of fine particles 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 energizing means”.

  As described above, in the present embodiment, after the operation of the engine (internal combustion engine) is started, the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is allowed prior to the start of driving of the particulate sensor 10. It is inspected whether or not it is within the range (specifically, whether or not the leakage current Im flowing between the inner metal fitting 20 and the outer metal fitting 70 is equal to or less than the reference value Ims).

When it is determined that the degree of insulation is within an allowable range (specifically, the leakage current Im is equal to or less than 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 greater 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 water, the particulate sensor 10 is driven to detect the amount of particulate S.
Therefore, according to the particulate detection system 1 of the present embodiment, after the operation of the engine (internal combustion engine) is started, the amount of the particulate S in the exhaust gas EG exhausted from the engine can be detected appropriately.

In the above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof.
For example, in the embodiment, the heating resistor 106 made of tungsten is used, but the constituent material of the heating resistor 106 is not limited to this. 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 flow of particle detection, but the flow of particle detection is not limited to this, for example, in the embodiment, only once 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 an allowable range (specifically, whether or not it is less than a preset reference value Ims). When the magnitude of the current Im is within the allowable range, the particle sensor 10 is driven in step S3. That is, whether or not the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is within the allowable range is determined based on the measurement result of the leakage current Im only once.
However, the leakage current Im is measured a plurality of times, and it is determined whether or not the degree of insulation between the inner metal fitting 20 and the outer metal fitting 70 is within an allowable range based on the measurement results obtained a plurality of times. good. For example, when the leakage current Im is measured three times and the magnitude of the leakage current Im is within an allowable range in all three times (specifically, it is equal to or less than a preset reference value Ims), the inner metal fitting 20 It may be determined that the degree of insulation between the outer metal fitting 70 and the outer metal fitting 70 is within an allowable range, and the particulate sensor 10 may be driven in step S3. In this way, by determining whether or not the degree of insulation is within the allowable range based on the measurement results of the leakage current Im multiple times, the reliability of the insulation determination can be improved, and thus the particle detection Can improve the reliability.

1 Particulate Detection System 10 Particulate Sensor 20 Inner Bracket 25 Gas Intake Pipe (Inner Bracket)
30 Main metal fitting (inner metal fitting)
40 Inner cylinder (inner metal fittings)
50 Inner tube fitting (inner fitting)
60 Inner protector (inner bracket)
60e Gas outlet 65 Outer protector (inner bracket)
65c Gas inlet 70 Outer bracket 80 Mounting bracket (Outer bracket)
90 Outer cylinder (outer bracket)
100 Insulating spacer 100k In-sensor exposed portion 101 Spacer main body 102 Layered heater portion 105 Spacer heater (heater)
106 Heating resistor 120 Ceramic element 130 Discharge electrode body 140 Auxiliary electrode body 200 Circuit unit 210 Ion source power supply circuit (sensor driving means)
221 Microprocessor (insulation test means, sensor drive means, heater energization means)
223 First heater heating circuit (heater energizing means)
230 Signal current detection circuit (insulation test means)
240 Auxiliary electrode power circuit (sensor drive means)
CP ion EP exhaust pipe (venting pipe)
EG Exhaust gas (measured gas)
EGI Intake gas Is Signal current PVE Ground potential PV1 First potential S Particle SC Charged particle SIS Sensor internal space t1 First time

Claims (3)

In the particulate detection system for detecting particulates contained in the gas to be measured flowing through the ventilation pipe,
A particulate sensor attached to the vent pipe having a ground potential;
Sensor driving means for driving the fine particle sensor,
The particulate sensor
A cylindrical outer metal fitting attached to the vent pipe and having the ground potential;
A first electric potential different from the ground potential, and an inner metal fitting surrounded by the outer metal fitting in the radial direction;
A cylindrical insulating spacer that is interposed between the inner metal fitting and the outer metal fitting to electrically insulate both;
The insulating spacer is
An exposed part in the sensor that is exposed in the sensor internal space surrounded by the outer metal fitting outside the vent pipe;
A heater for heating the exposed portion in the sensor,
The heater includes a heating resistor embedded in the insulating spacer,
The particulate detection system includes:
Insulation inspection means for inspecting whether or not the degree of insulation between the inner metal fitting and the outer metal fitting is within an allowable range;
Heater energization means for energizing the heater to generate heat in the heating resistor,
The heater energizing means includes
When the insulation test means determines that the degree of insulation is not within the allowable range, the heater is expected to remove water adhering to the surface of the exposed portion in the sensor. Energize for 1 hour, energize the first heater,
The sensor driving means includes
A fine particle detection system that drives the fine particle sensor after the insulation test means determines that the degree of insulation is within the allowable range or after the first heater energization is completed. The particulate detection system according to claim 1,
The fine particle sensor is driven by the sensor driving means to generate an air discharge, and ions generated by the air discharge are attached to the fine particles contained in the gas to be measured to be charged charged fine particles. And detecting the amount of the fine particles in the gas to be measured using a signal current flowing in accordance with the amount of the charged fine particles between the first potential and the ground potential. The fine particle detection system according to claim 1 or 2,
The vent pipe is an exhaust pipe of an internal combustion engine,
The gas to be measured is exhaust gas,
After the operation of the internal combustion engine is started, the insulation test means has a degree of insulation between the inner metal fitting and the outer metal fitting before starting the driving of the particulate sensor by the sensor driving means. A particulate detection system for inspecting whether or not the tolerance is within the allowable range.

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