JP2012251926A - Fine particle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine particle sensor having a simplified new structure.SOLUTION: The fine particle sensor includes: an insulative casing extending in an axial direction, having an inflow hole and an outflow hole; a corona discharging part for generating an ion; a mixing part for mixing the ion with a fine particle flowing into the casing through the inflow hole; and a separating part located at one end side closer than from the mixing part to separate an adsorbed ion used for charging the fine particle from a floating ion unused for charging the fine particle. The separating part has a separating electrode arranged on an inner face of the casing to generate repulsive force with the floating ion therebetween, and a separating counter electrode arranged on an opposite side inner face confronting the separating electrode in the inner face of the casing to generate attraction force with the floating ion therebetween.

Description

  The present invention relates to a particulate sensor for detecting particulates such as soot contained in exhaust gas.

  The exhaust gas from an internal combustion engine such as a diesel engine contains particulates such as soot. Here, a fine particle sensor is known that is attached to an exhaust gas pipe and detects the amount of soot in the exhaust gas (for example, Patent Document 1). This particulate sensor is used, for example, to determine whether or not the particulate collection filter provided in the previous stage of the particulate sensor is functioning normally.

  The fine particle sensor disclosed in Patent Document 1 charges the soot using ions generated by corona discharge, and then separates ions adsorbed on the soot from ions not adsorbed on the soot. The amount of soot is detected based on the difference in charge amount between the ions adsorbed on the soot and the ions not adsorbed on the soot.

International Publication WO2009 / 109688 JP-T-2007-514923

  However, the fine particle sensor needs to include an electrode for generating a corona discharge, a member for separating ions adsorbed on the soot that is fine particles and ions not adsorbed, and the like. For this reason, in the conventional fine particle sensor, the sensor itself has a complicated structure, and the manufacturing process may be complicated. Such a problem is not limited to the particulate sensor used to detect the amount of soot in the exhaust gas, but is a problem common to the particulate sensor used to detect the amount of particulate contained in the gas to be detected. Met.

  Accordingly, an object of the present invention is to provide a particulate sensor having a new and simplified structure.

[Application Example 1] In order to detect the amount of fine particles contained in the gas to be detected, the fine particles are charged using ions generated by corona discharge, and the adsorbed ions and the ions used for charging are charged. In the fine particle sensor that separates floating ions that are not used,
An insulating casing extending in the axial direction, an inflow hole for allowing the detection gas to flow into the inside, and one end side of the inflow hole for allowing the detection gas to flow out A casing having an outflow hole;
A corona discharge part formed in the casing and generating the ions by the corona discharge;
A mixing unit that is formed in the casing at a position closer to the one end than the corona discharge unit, and mixes the ions and the fine particles flowing into the casing through the inflow hole;
A separation part that is formed in the casing and separates the adsorbed ions and the floating ions at a position closer to the one end than the mixing part;
The separation unit is
A separation electrode disposed on an inner surface of the casing, the separation electrode generating a repulsive force with the floating ions;
A separation counter electrode disposed on an inner surface of the casing opposite to the separation electrode, the separation counter electrode generating an attractive force with the floating ions. Fine particle sensor.

  Here, when the separation electrode and the separation counter electrode are arranged at a position away from the inner surface of the casing, for example, in the vicinity of the central axis of the casing, the particle sensor has sufficient space for arranging each electrode inside the casing. It may be necessary to provide the structure, or it may be necessary to have a complicated structure so that each pole and another member are not in contact with each other and short-circuited. According to the fine particle sensor described in Application Example 1, the separation electrode and the separation counter electrode in the separation portion are arranged on the inner surface of the insulating casing. Therefore, the structure of the particle sensor can be simplified as compared with the case where each pole is arranged away from the inner surface of the casing. Further, the separation electrode and the separation counter electrode can be easily provided as constituent members of the fine particle sensor.

[Application Example 2] In the fine particle sensor according to Application Example 1,
The casing is
Having first and second casings respectively extending in the axial direction;
The separation electrode is disposed on the inner surface of the first casing,
The separation counter electrode is disposed on the inner surface of the second casing,
The casing is formed by adhering the first and second casings to each other in a state where the separation electrode and the separation counter electrode face each other.
According to the particulate sensor described in Application Example 2, the separation electrode is disposed on the inner surface of the first casing, the separation counter electrode is disposed on the inner surface of the second casing, and the first and second casings are disposed. By adhering, a fine particle sensor including a separation electrode and a separation counter electrode arranged to face each other on the inner surface of the casing can be easily manufactured. That is, according to the particulate sensor described in Application Example 2, the separation electrode and the separation counter electrode can be easily disposed on the inner surface of the casing. In fixing the first and second casings, for example, a ceramic adhesive or a glass paste is applied to the overlapping surface (bonding surface) where the first and second casings are overlapped with each other. It ’s fine.

[Application Example 3] In the fine particle sensor according to Application Example 1 or Application Example 2,
The separation part is a narrow flow path having a smaller cross-sectional area perpendicular to the axial direction than the mixing part, and has the narrow flow path in which the separation electrode and the separation counter electrode are respectively disposed on the inner surface. A fine particle sensor characterized by that.
According to the fine particle sensor described in Application Example 3, the separation unit has a narrow channel in a part of the axial direction, so that the ions (floating ions) that do not adhere to the microparticles compared with the case where the separation unit does not have the narrow channel. ) With greater repulsive force and attractive force. As a result, more floating ions can be reliably moved to the separation counter electrode, and the floating ions can be efficiently captured by the separation counter electrode.

[Application Example 4] In the fine particle sensor according to any one of Application Examples 1 to 3,
The corona discharge part is
A discharge electrode disposed on the inner surface of the other end side at a position not overlapping with the separation electrode and the separation counter electrode, of the inner surface of the casing;
A fine particle sensor comprising: a discharge counter electrode that is a counter electrode of the discharge electrode, and that generates a corona discharge with the discharge electrode.
According to the particulate sensor described in Application Example 4, the discharge electrode is also disposed on the inner surface of the casing. Therefore, the structure of the fine particle sensor can be further simplified. Further, the discharge electrode can be easily provided as a constituent member of the fine particle sensor.

Application Example 5 In the fine particle sensor according to Application Example 4,
The inflow hole is formed in a portion of the casing that defines the mixing portion,
The particulate sensor further includes:
A conductive nozzle forming member that forms a nozzle opening that opens in the axial direction at a position between the discharge electrode and the mixing portion in the axial direction;
The fine particle sensor, wherein the nozzle forming member functions as the discharge counter electrode.
According to the particulate sensor described in Application Example 5, the nozzle sensor includes a nozzle forming member in which a nozzle opening is formed at a position between the discharge electrode and the mixing unit. Thereby, it becomes possible to inject air into a mixing part from a nozzle opening. That is, by making the mixing part have a negative pressure, the gas to be detected can be easily taken into the mixing part through the inflow hole. Further, by using the nozzle forming member for making the mixing part have a negative pressure also as the counter electrode for discharge, the number of parts can be reduced and the structure of the fine particle sensor can be further simplified.

[Application Example 6] In the particle sensor according to Application Example 5,
A gas supply flow path formed in the casing on the other end side of the nozzle opening, the gas supply flow for circulating an external gas blown from the other end side of the nozzle opening to the nozzle opening side A particle sensor characterized by having a path.
According to the particulate sensor described in the application example 6, the gas sensor has the gas supply flow channel for circulating the gas from the outside sprayed to the nozzle opening. Thereby, gas can be sprayed to a nozzle opening from the other end side of a nozzle opening, without providing gas supply flow paths, such as a supply pipe | tube, outside the particulate sensor. Therefore, the mixing part can be easily made a negative pressure, and the gas to be detected can be stably taken into the mixing part via the inflow hole.

Application Example 7 In the fine particle sensor according to any one of Application Examples 1 to 6,
A fine particle sensor comprising an insulating protective member disposed on the separation electrode and protecting the separation electrode.
According to the fine particle sensor described in Application Example 7, since the separation electrode is covered with the insulating protective member, it is possible to reduce the possibility that the separation electrode is electrically connected to another member and short-circuit occurs.

[Application Example 8] In the fine particle sensor according to any one of Application Examples 1 to 7,
At least one of the separation electrode and the separation counter electrode is formed by applying and baking a conductive paste on the inner surface of the casing.
According to the fine particle sensor described in Application Example 8, at least one of the separation electrode and the separation counter electrode can be easily arranged on the inner surface of the casing by applying and baking the conductive paste on the inner surface of the casing.

[Application Example 9] In the fine particle sensor according to any one of Application Example 4 to Application Example 6, Application Example 7 or Application Example 8 subordinate to Application Example 4,
The fine particle sensor, wherein the discharge electrode is formed by applying and baking a conductive paste on an inner surface of the casing.
According to the fine particle sensor described in Application Example 9, the discharge electrode can be easily disposed on the inner surface of the casing by applying and baking the conductive paste on the inner surface of the casing.

[Application Example 10] In the fine particle sensor according to any one of Application Examples 1 to 9,
A fine particle sensor comprising a protective outer cylinder surrounding an outer periphery of a portion of the casing exposed to the detected gas and having an opening for circulating the detected gas.
According to the particulate sensor described in Application Example 10, by providing the protective outer cylinder, it is possible to prevent the casing from being damaged when the particulate sensor is attached to a flow pipe or the like through which the gas to be detected flows. Moreover, even when a liquid such as water is contained in the gas to be detected, it is possible to suppress the liquid from adhering to the casing.

  Note that the present invention can be realized in various forms, and can be realized, for example, in the form of a particle sensor, a method for manufacturing the particle sensor, a vehicle equipped with the particle sensor, and the like.

It is a figure for demonstrating the vehicle carrying the particulate sensor as an Example of this invention. 2 is a schematic view of a tip portion 100e of the particle sensor 100. FIG. 1 is a first cross-sectional view of a particle sensor 100. FIG. 3 is a second cross-sectional view of the particle sensor 100. FIG. 2 is an exploded perspective view of the particle sensor 100. FIG. 2 is a schematic cross-sectional view showing a configuration of a cable 120. FIG. It is the schematic for demonstrating the detection method of the amount of soot by the sensor control part.

Next, embodiments of the present invention will be described in the following order.
A. Example:
B. Variations:

A. Example:
A-1: Overall configuration of the particle sensor:
FIG. 1 is a diagram for explaining a vehicle equipped with a particle sensor as an embodiment of the present invention. FIG. 1A is a schematic configuration diagram of a vehicle on which a particle sensor is mounted. FIG. 1 (B) is a diagram showing the state of attachment of the particulate sensor to the exhaust gas pipe 415 of the vehicle and the internal configuration of the sensor driving unit. Here, in the fine particle sensor, the lower side of the sheet of FIG. 1B is also referred to as “one end side (front end side)”, and the upper side of the sheet of FIG. 1B is also referred to as “other end side (rear end side)”.

  As shown in FIG. 1A, the vehicle 500 includes an internal combustion engine 400, a fuel supply unit 410, and a vehicle control unit 420. The internal combustion engine 400 is a power source of the vehicle 500, and can be constituted by, for example, a diesel engine. The fuel supply unit 410 supplies fuel to the internal combustion engine 400 via the fuel pipe 411.

  The vehicle control unit 420 can be configured by a microcomputer and controls the driving state of the entire vehicle 500. Specifically, the vehicle control unit 420 controls the combustion state of the fuel in the internal combustion engine 400, the amount of fuel supplied from the fuel supply unit 410, and the like. An exhaust gas pipe 415 is connected to the internal combustion engine 400, and exhaust gas from the internal combustion engine 400 is discharged to the outside of the vehicle 500 through the exhaust gas pipe 415. The exhaust gas pipe 415 is provided with a filter device 416 (for example, DPF (Diesel particulate filter)) for removing particulates such as soot contained in the exhaust gas.

  The vehicle 500 is further equipped with a sensor system 130 that detects the amount of fine particles in the exhaust gas. The sensor system 130 includes a particle sensor 100, a sensor driving unit 110, and a cable 120 that connects the particle sensor 100 and the sensor driving unit 110. The particulate sensor 100 is attached to the downstream side of the filter device 416 of the exhaust gas pipe 415. It can be said that the cable 120 is one of the constituent members of the particle sensor 100.

  The fine particle sensor 100 charges the soot, which is a fine particle, using ions (in this embodiment, positive ions) generated by corona discharge. The fine particle sensor 100 separates cations used for charging (also referred to as “adsorption cations”) and cations that were not used for charging (also referred to as “floating cations”). A detection signal for detecting the amount of soot is output to the sensor driving unit 110. Details of the particle sensor 100 will be described later.

  The sensor driving unit 110 drives the particulate sensor 100 and detects the amount of soot in the exhaust gas based on the detection signal from the particulate sensor 100. For example, the vehicle control unit 420 diagnoses the performance of the filter device 416 based on the detected soot amount. For example, when the detected soot amount exceeds a predetermined value, the vehicle control unit 420 determines deterioration or abnormality of the filter device 416 and notifies the user by displaying the determination result on a monitor. Here, the amount of soot in the exhaust gas may be, for example, in units of surface area or in units of mass. Alternatively, the amount of soot in the exhaust gas may be based on the number of soot, or the concentration of soot in the exhaust gas.

  As shown in FIG. 1B, the particle sensor 100 extends in the direction of the axis CL. In the particulate sensor 100, a tip end portion 100e located on one end side is inserted into the exhaust gas pipe 415 and exposed to the exhaust gas flowing through the exhaust gas pipe 415. An opening for taking exhaust gas into the inside of the particle sensor 100 is formed on the tip side of the particle sensor 100. Details of this will be described later.

  A flexible cable 120 is connected to the other end of the particle sensor 100. The cable 120 is extended and connected to the sensor driving unit 110 while being flexibly deformed to the sensor driving unit 110. The sensor driving unit 110 includes a sensor control unit 111, an electric circuit unit 112, and an air supply unit 113.

  The sensor control unit 111 can be configured by a microcomputer, and controls the electric circuit unit 112 and the air supply unit 113 and transmits a detection result using the particle sensor 100 to the vehicle control unit 420.

  The electric circuit unit 112 supplies power for driving the particle sensor 100 via the electric wiring group EW housed in the cable 120 and receives a sensor signal of the particle sensor 100. The electrical wiring group EW includes a plurality of electrical wirings (signal lines). The sensor control unit 111 detects the amount of soot contained in the exhaust gas based on the sensor signal received by the electric circuit unit 112. Details of this detection method will be described later.

  The air supply unit 113 includes a pump (not shown). The air supply unit 113 supplies high-pressure air used when driving the particle sensor 100 to the particle sensor 100 through the air supply pipe 123 accommodated in the cable 120 based on a command from the sensor control unit 111.

A-2. Schematic configuration of the particle sensor 100:
Before explaining the detailed configuration of the particle sensor 100, the schematic configuration of the particle sensor 100 will be described for easy understanding. FIG. 2 is a schematic view of the tip portion 100e of the particle sensor 100. FIG.

  The fine particle sensor 100 includes a bottomed cylindrical casing 24 having insulating properties. The casing 24 is made of an insulating ceramic having heat resistance such as alumina. The particulate sensor 100 is formed with an inflow hole 45 for allowing the exhaust gas to flow into the casing 24 and one end side (the tip side in the direction of the axis CL) of the inflow hole 45, and an outflow for allowing the exhaust gas to flow outside. And a hole 35. The inflow hole 45 and the outflow hole 35 are formed on the side surface of the casing 24. Further, the particle sensor 100 includes a corona discharge unit 72, a mixing unit 71, and a separation unit 31 in order from the other end side to the one end side. Each part 72, 71, 31 is formed in the casing 24. Further, on the inner surface of the casing 24, a first conductive member 10V and a second conductive member 11V are arranged. The first and second conductive members 10V and 11V are disposed on the inner surface of the casing 24 by applying and baking a conductive paste containing metal particles such as copper and an organic solvent on the inner surface of the casing 24, for example. . When power is supplied from the electric circuit unit 112, the first conductive member 10V functions as an anode, and the second conductive member 11V functions as a cathode. Further, one end side of the first conductive member 10V functions as a separation electrode 10 described later. One end side of the second conductive member 11V functions as a separation counter electrode 11 to be described later.

  The fine particle sensor 100 is attached to the insulating casing 24 and has a conductive nozzle forming member 41 positioned between the mixing portion 71 and a discharge electrode 20 described later in the direction of the axis CL. The nozzle forming member 41 is made of metal such as stainless steel. The nozzle forming member 41 has a disc shape, and a nozzle opening 42 that opens in the direction of the axis CL (the vertical direction in FIG. 2) is formed in the approximate center. The nozzle forming member 41 is electrically connected to the second conductive member 11V and is not electrically connected to the first conductive member 10V.

  The corona discharge part 72 has the discharge electrode 20 that functions as an anode. The discharge electrode 20 is disposed on the inner surface of the casing 24 by applying a conductive paste on the inner surface of the casing 24 and baking it. The conductive paste contains, for example, metal particles such as copper and an organic solvent. Here, the nozzle forming member 41 functions as a counter electrode for discharge which is a counter electrode of the electrode 20 for discharge. Therefore, the nozzle forming member 41 is also referred to as a discharge counter electrode 41. The corona discharge unit 72 generates a corona discharge between the discharge electrode 20 and the discharge counter electrode 41. As will be described later with reference to FIG. 5, the one end portion 20 </ b> S of the discharge electrode 20 has a shape in which the width decreases toward the one end side and the one end is pointed. Then, when corona discharge is generated in the corona discharge unit 72, the discharged electrons collide with molecules in the air supplied to the corona discharge unit 72, and ions (positive ions) 80 are generated in the surroundings.

  The positive ions 80 generated in the corona discharge part 72 are jetted from the nozzle opening 42 to the mixing part 71 together with the high-pressure air supplied from the other end side of the nozzle opening 42 by the air supply part 113 (FIG. 1). Thereby, the mixing part 71 becomes a negative pressure. For example, the pressure of the air supplied to the fine particle sensor 100 is preferably set to a pressure at which the air injection speed from the nozzle opening 42 is about the speed of sound. The high-pressure air flows through the gas supply channel 700 formed in the particle sensor 100 and is blown to the nozzle opening 42.

  An inflow hole 45 is formed in a portion of the insulating casing 24 that defines the mixing portion 71. That is, the inflow hole 45 communicates directly with the mixing unit 71. The mixing portion 71 becomes negative pressure when high-pressure air is injected from the nozzle opening 42, and the exhaust gas to be detected can be satisfactorily and stably taken into the casing 24 through the inflow hole 45. it can. The cations 80 that have flowed into the mixing portion 71 through the nozzle opening 42 and the exhaust gas that has flowed into the mixing portion 71 through the inflow hole 45 are mixed by the mixing portion 71. As a result, when the soot 82 which is fine particles is present in the exhaust gas, the cation 80 is adsorbed on the soot 82 and charged.

  On the inner surface of the insulating casing 24, a first conductive member 10V and a second conductive member 11V are arranged. Specifically, the first and second conductive members 10 </ b> V and 11 </ b> V extend in the axis CL direction from one end of the casing 24 to the other end.

  The separation unit 31 includes a separation electrode 10 that functions as an anode and a separation counter electrode 11 that functions as a cathode. The separation electrode 10 generates a repulsive force with the cation 80 (particularly, the floating cation 80). The separation counter electrode 11 generates an attractive force with the cation 80 (particularly, the floating cation 80). The separation electrode 10 is a portion of the first conductive member 10 </ b> V that is disposed on one end side of the mixing portion 71 and expands in a planar shape. The separation counter electrode 11 is a portion of the second conductive member 11V that is disposed on one end side with respect to the mixing portion 71 and expands in a planar shape. Details of the separation electrode 10 and the separation counter electrode 11 will be described later.

  The separation unit 31 includes a first flow path 31a, a narrow flow path 31c, and a second flow path 31b in order from the other end side toward the one end side along the axis line CL direction. As for the 1st flow path 31a, opening area (cross-sectional area orthogonal to an axis line CL direction) reduces gradually as it goes to one end side from the other end side. The narrow channel 31 c has a constant opening area smaller than that of the mixing unit 71. The opening area of the second flow path 31b gradually expands from the other end side toward the one end side. Outflow holes 35 are formed in the wall surface of the portion of the casing 24 that forms the second flow path 31b.

  Here, the cation 80 (floating cation 80) that has not been adsorbed on the ridge 82 moves away from the separation electrode 10. That is, due to the repulsive force by the separation electrode 10 and the attractive force by the separation counter electrode 11, the floating cation 80 advances in the direction in which the separation counter electrode 11 is positioned regardless of the flow of the exhaust gas. The floating cation 80 colliding with the separation counter electrode 11 is captured by the separation counter electrode 11. On the other hand, the cation 80 (adsorption cation 80) adsorbed on the cage 82 has a considerably larger mass than the floating cation 80. For this reason, the influence of external electrical repulsive force or attractive force is smaller than that of the floating cation 80. Therefore, even if it receives an electric force, it is discharged from the outflow hole 35 to the outside by the flow of the exhaust gas. Thereby, the floating cation 80 and the adsorbed cation 80 are separated in the casing 24.

A-3. Detailed configuration of the particle sensor 100:
The detailed configuration of the particle sensor 100 will be described with reference to FIGS. FIG. 3 is a first cross-sectional view of the particle sensor 100. FIG. 4 is a second cross-sectional view of the particle sensor 100. FIG. 5 is an exploded perspective view of the particle sensor 100. Here, FIG. 4 is a 3-3 cross-sectional view of FIG. 3 and 4 have XYZ axes orthogonal to each other.

  As shown in FIGS. 3 to 5, the particle sensor 100 includes an insulating ceramic casing 24 that extends in the direction of the axis CL, and an outer periphery on one end that is a portion of the casing 24 that is exposed to exhaust gas that is a detected gas. The surrounding first outer cylinder 22 (protective outer cylinder 22), the joint part 103 connected to the other end of the first outer cylinder 22, and the second outer cylinder 360 connected to the other end side of the joint part 103 With. The first outer cylinder 22, the joint portion 103, and the second outer cylinder 360 are made of metal such as stainless steel. The first outer cylinder 22 has a plurality of openings 22a in the circumferential direction for allowing the exhaust gas to flow therethrough. Further, the one end surface 22 b of the first outer cylinder 22 constitutes one end of the particle sensor 100. Here, by installing the first outer cylinder 22, it is possible to prevent the casing 24 made of insulating ceramic from being damaged when the particulate sensor 100 is attached to the exhaust gas pipe 415. Moreover, it can suppress that liquids, such as water contained in waste gas, adhere to the casing 24. FIG.

  A tool engaging part 104 for engaging with a tool such as a hexagon wrench is provided on the outer periphery of the joint part 103. A gasket 64 is attached to one end surface of the tool engaging portion 104. The gasket 64 attaches the particulate sensor 100 to the exhaust gas pipe 415 in an airtight manner so that the exhaust gas does not leak outside from the exhaust gas pipe 415.

  As shown in FIG. 5, the casing 24 includes a first casing 27 and a second casing 29 that are divided in the direction of the axis CL. That is, the casing 24 includes first and second casings 27 and 29 that are divided by a predetermined plane including the axis CL. The first and second casings 27 and 29 each extend in the direction of the axis CL. The first and second casings 27 and 29 are fixed by applying and adhering a heat-resistant ceramic adhesive mainly composed of alumina to the overlapping surfaces (bonding surfaces). Specifically, the first and second casings 27 and 29 are placed in a state where the separation electrode 10 disposed in the first casing 27 and the separation counter electrode 11 disposed in the second casing 29 face each other. The casing 24 is formed by being fixed to each other using a ceramic adhesive.

  As shown in FIGS. 3 and 4, a fixing member 320 formed in a cylindrical shape is fitted on the other end side of the casing 24. Thereby, the fixing member 320 and the casing 24 are integrated. The fixing member 320 is made of a metal such as stainless steel. The fixing member 320 is mounted inside the joint portion 103 so that one end side of the casing 24 protrudes from the tip of the joint portion 103 and is exposed to the exhaust gas, whereby the casing 24 is interposed between the fixing member 320 and the joint portion 103. It is held and held with respect to the joint portion 103. Although not shown in FIG. 5, the fixing member 320 has a male screw portion formed on the outer periphery, and the fixing member 320 is screwed into a female screw portion formed on the inner periphery of the joint portion 103. Both 103 and 320 are fixed to each other.

  As shown in FIG. 3, the cable 120 is attached to the other end side of the second outer cylinder 360. An annular grommet 350 for protecting the cable 120 is disposed between the cable 120 and the second outer cylinder 360. In the cable 120, various electric wirings including the first and second shield lines SL1 and SL2 and an air supply pipe 123 are formed. The other end side of the second outer cylinder 360 is crimped to hold the cable 120, and a crimped portion 360c is formed. At the time of this caulking, a cut is provided in the outer skin 1204 of the cable 120, and a part of the second outer cylinder 306 is caused to enter the cut. As a result, the caulking portion 360c is electrically connected to the second shield line SL2 of the cable 120. The other end 360 b of the second outer cylinder 360 constitutes the other end of the particle sensor 100.

  As shown in FIG. 5, the first conductive member 10 </ b> V is disposed on the inner surface of the portion of the first casing 27 when assembled as the casing 24. An insulating member 14V is disposed on the first conductive member 10V. The insulating member 14 </ b> V is disposed on the first conductive member 10 </ b> V by applying and baking an insulating insulating paste containing ceramic and an organic solvent on the first conductive member 10 </ b> V. Of the portion of the second casing 29, the second conductive member 11 </ b> V is disposed on the inner surface when assembled as the casing 24.

  The first conductive member 10 </ b> V includes a linear lead portion 132 located on the other end side and the separation electrode 10 located on one end side and connected to the lead portion 132. The lead part 132 is joined to the terminal 302 by brazing, and is connected to a first insulating wiring (described later) in the cable 120 via the terminal 302. Thereby, the first conductive member 10V is electrically connected to the sensor driving unit 110 (FIG. 1A). As shown in FIG. 5, the separation electrode 10 has a planar shape, and is disposed on the inner surface of the first casing 27 with a circumferential width. Specifically, as shown in FIG. 4, the separation electrode 10 is disposed on the inner surfaces of the narrow channel 31c and the second channel 31b.

  As shown in FIG. 5, the insulating member 14 </ b> V includes a linear first protective member 142 disposed so as to overlap the lead portion 132 and a planar first member disposed so as to overlap the separation electrode 10. 2 protective members 14. The fine particle sensor 100 has the insulating member 14V, so that fine particles such as soot are deposited on the first conductive member 10V, and the other conductive member (for example, the nozzle forming member 41) and the first conductive member 10V. Can reduce the possibility of short circuit. Thereby, the fall of the detection accuracy of the quantity of particulates of particulate sensor 100 can be controlled. The first protection member 142 is shorter than the lead portion 132, and the other end side of the lead portion 132 is exposed without being covered by the first protection member 142. Thereby, the other end side of the lead part 132 is joined to the terminal 302. Here, the “second protective member 14” corresponds to the “protective member” described in the means for solving the problem.

  As shown in FIG. 5, the second conductive member 11 </ b> V includes a linear lead portion 152 located on the other end side and a separation counter electrode 11 located on the one end side and connected to the lead portion 152. As shown in FIG. 4, the lead portion 152 is brazed to the terminal 301, and a first wire in the cable 120 is connected via a lead wire 324 connected to the terminal 301 and a joint portion 326 to which the lead wire 324 is connected. And the shield line SL1. Accordingly, the second conductive member 11V is electrically connected to the sensor driving unit 110 (FIG. 1A). Note that one end side of the first shield line SL1 is exposed to the outside from the cable 120, and the exposed portion is connected to the joint portion 326. Further, the lead wire 324 is connected to a protruding portion 326 a that protrudes to one end side of the joint portion 326.

  The separation counter electrode 11 has a planar shape, and is disposed on the inner surface of the second casing 29 with a circumferential width. Specifically, as shown in FIG. 3, the separation counter electrode 11 is disposed on the inner surface of the separation portion 31. Further, the separation counter electrode 11 and the separation electrode 10 are disposed so as to face each other.

  As shown in FIGS. 3 and 5, on the inner surface (on the other end side inner surface) of the inner surface of the second casing 29 at a position that does not overlap the first and second conductive members 10 </ b> V and 11 </ b> V, Discharge electrodes 20 are arranged. The discharge electrode 20 has a planar shape and is located on the other end side with respect to the separation electrode 10 and the separation counter electrode 11. The other end side of the discharge electrode 20 is connected to a second insulated wire (described later) in the cable 120 via a terminal 304 fitted in the opening on the other end side of the casing 24. Thereby, the electrode 20 for discharge is electrically connected with the sensor drive part 110 (FIG. 1 (A)). As shown in FIG. 4, the terminals 301, 302, and 304 are arranged in the second outer cylinder 360 with a space therebetween so that they do not contact each other.

  As shown in FIG. 3, a disc-shaped nozzle forming member 41 is disposed between the discharge electrode 20 and the mixing portion 71 in the axis CL direction of the casing 24. The nozzle forming member 41 is made of metal (for example, stainless steel) and has conductivity. The nozzle forming member 41 partitions the corona discharge part 72 and the mixing part 71. As shown in FIG. 5, the nozzle forming member 41 has a protruding portion 43 that protrudes radially outward from the outer peripheral surface. When the protruding portion 43 comes into contact with the lead portion 152, the nozzle forming member 41 and the second conductive member 11V are electrically connected. The nozzle forming member 41 and the first conductive member 10V are arranged at a predetermined interval so that the nozzle forming member 41 and the first conductive member 10V are not in contact with each other.

  A nozzle opening 42 that opens in the direction of the axis CL is formed in the approximate center of the nozzle forming member 41. The nozzle opening 42 is a minute hole (orifice). In this embodiment, the diameter of the corona discharge part 72 is about 10 mm, whereas the diameter of the nozzle opening 42 is about 0.3 mm. As described above, since the nozzle opening 42, which is a minute hole, is formed in the metal nozzle forming member 41, it can be formed with higher accuracy than that formed in the ceramic member.

  The nozzle forming member 41 can make the mixing portion 71 located at one end side of the nozzle opening 42 to have a negative pressure. Specifically, high-pressure gas (air in the present embodiment) of atmospheric pressure or higher is blown from the other end side of the nozzle opening 42 to the nozzle opening 42, so that gas is injected into the mixing unit 71 and the mixing unit 71 is Negative pressure. Further, a predetermined voltage is applied between the discharge electrode 20 and the nozzle forming member 41 by the sensor driving unit 110 (FIG. 1B), so that the one end 20S of the discharge electrode 20 and the nozzle forming member are applied. Corona discharge occurs between the surface of the 41 facing the corona discharge portion 72.

  As shown in FIG. 3, an air supply pipe 123 extending in the direction of the axis CL is formed in the cable 120. As shown in FIG. 4, a through hole 308 extending in the direction of the axis CL is formed in the terminal 304. In the air supply pipe 123, the internal space of the second outer cylinder 360, the through hole 308, and the internal space of the casing 24, a gas supply flow path 700 (in which air blown from the air supply part 113 toward the nozzle opening 42 circulates). FIG. 2) is formed.

  FIG. 6 is a schematic cross-sectional view showing the configuration of the cable 120 connected to the particle sensor 100 of the present embodiment. In the cable 120, the first and second insulated wires 121 and 122, the air supply pipe 123, and the first and second shield wires SL1 and SL2 are integrally accommodated. More specifically, the cable 120 has the following configuration.

  The first insulated wire 121 has a core wire 1210 that is a conductive wire at the center thereof. A first resin coating layer 1211 made of a fluorine-based resin such as FEP (tetrafluoroethylene / hexafluoropropylene copolymer) is provided on the outer periphery of the core wire 1210.

  The second insulated wire 122 also has a configuration similar to that of the first insulated wire 121, and includes a core wire 1220 that is a conductive wire and a first resin coating layer 1221 that covers the outer periphery thereof. The air supply pipe 123 is made of a resin member such as PTFE (polytetrafluoroethylene). The outer periphery of the air supply pipe 123 is covered with a reinforcing member 123s. The reinforcing member 123s can be formed of a braided metal wire.

  A glass fiber portion 1201 filled with glass fibers is formed on the outer periphery of the reinforcing members 123 s of the first and second insulated wires 121 and 122 and the air supply pipe 123. And the outer periphery of the glass fiber part 1201 is coat | covered with the 1st resin coating layer 1202. The first resin coating layer 1202 can be made of a resin member such as PTFE.

  A first shield line SL1 in which conductive wires are braided is disposed on the outer periphery of the first resin coating layer 1202, and the outside of the first shield line SL1 is configured by a resin member such as PTFE. A second resin coating layer 1203 is provided. A second shield line SL2 in which conductive wires are braided is disposed on the outer periphery of the second resin coating layer 1203, and the outer periphery of the second shield line SL2 is made of a fluorine-based resin such as FEP. The outer skin 1204 is covered.

  Thus, in this cable 120, the first and second shield lines SL1 and SL2 are provided in duplicate. Among these, the first shield line SL1 is electrically connected to the second conductive member 11V. Thus, the first shield line SL1 functions as a signal line that connects the tip portion 100e of the particle sensor 100 and the electric circuit portion 112. On the other hand, as described above, the second shield line SL2 is electrically connected to the crimped portion 360c of the second outer cylinder 360 that penetrates the outer skin 1204. Then, it is grounded by being electrically connected to a chassis (not shown) of the vehicle 500 through the second outer cylinder 360, the joint portion 103, and the exhaust gas pipe 415.

  Here, as described above, the cable 120 accommodates the air supply pipe 123 for high-pressure air that is used when the particle sensor 100 is driven. Since the pressure of the air supplied to the particulate sensor 100 by the air supply pipe 123 is preferably as high as possible, the air supply pipe 123 is preferable as the pressure resistance is high. The cable 120 preferably has flexibility in order to improve the disposition of the particulate sensor 100 to the vehicle 500. Therefore, it is preferable that the air supply pipe 123 accommodated in the cable 120 is also made of a resin member so as to have flexibility.

  By the way, in general, the region near the exhaust gas pipe of the internal combustion engine may be extremely hot (for example, about 600 ° C.). Since the particulate sensor 100 of the present embodiment is attached to the exhaust gas pipe 415, the cable 120 connected to the particulate sensor 100 is also disposed in the vicinity of the exhaust gas pipe 415. However, when the cable 120 is disposed in a high temperature region in the vehicle 500 such as a region near the exhaust gas pipe 415, the air supply pipe 123 itself made of a resin member is caused by the rise in the temperature of the cable 120. It may be damaged.

  Therefore, in the cable 120 of the present embodiment, a flexible reinforcing member 123 s formed by braiding metal wires is provided on the outer periphery of the air supply pipe 123. The possibility that the air supply pipe 123 is damaged can be reduced by the reinforcing member 123s.

  As described above, the particle sensor 100 is driven by being connected to the sensor driving unit 110 by the cable 120 while the distal end portion 100e is inserted and disposed in the exhaust gas pipe 415. In the vehicle 500, the particulate sensor 100 is used to detect the amount of soot contained in the exhaust gas.

A-4. Detection method using the particle sensor 100:
FIG. 7 is a schematic diagram for explaining a method for detecting the amount of soot by the sensor control unit 111. FIG. 7 schematically illustrates the tip 100e of the particle sensor 100, the sensor control unit 111 of the sensor driving unit 110, and the electric circuit unit 112.

  The electric circuit unit 112 includes a primary power supply unit 210, a secondary power supply unit 220, and a current difference measurement unit 230. The primary-side power supply unit 210 supplies high-voltage power to the secondary-side power supply unit 220 through a transformer in accordance with a command from the sensor control unit 111. The secondary power supply unit 220 includes a first current supply circuit 221 and a second current supply circuit 222.

  The first current supply circuit 221 is connected to the first conductive member 10 </ b> V including the separation electrode 10 via the first insulated wire 121. The second current supply circuit 222 is connected to the discharge electrode 20 via the second insulated wire 122. That is, the particle sensor 100 receives power supply for capturing the positive ions 80 from the first current supply circuit 221 and supplies power for corona discharge that generates the positive ions 80 from the second current supply circuit 222. receive. The second current supply circuit 222 is a constant current circuit, and supplies a constant current Iin of, for example, about 5 μA to the discharge electrode 20 during corona discharge.

  The tip 100e of the particulate sensor 100 is held in the exhaust gas pipe 415 in a state insulated from the exhaust gas pipe 415 and the chassis of the vehicle 500. That is, it can be interpreted that the second conductive member 11V of the particulate sensor 100 has a reference potential different from the reference potential of the vehicle 500, which is also called a so-called chassis ground.

  When the input current Iin flows from the second current supply circuit 222 to the discharge electrode 20, the discharge current Idc flows from the discharge electrode 20 to the second conductive member 11V and positive ions 80 are generated due to corona discharge. A part of the generated cation 80 is used for charging the ridge 82, and the remaining cation 80 is captured by the separation counter electrode 11 in the separation unit 31.

The current corresponding to the flow of cations 80 used for charging the cage 82 and leaking out of the casing 24 is also referred to as “leakage current Iesc”. On the other hand, a current corresponding to the flow of positive ions 80 captured by the separation counter electrode 11 disposed on the inner surface of the casing 24 is also referred to as “capture current Itrp”. At this time, the following relational expression (1) is established for these four currents Iin, Idc, Iesc, and Itrp flowing by corona discharge.
Iin = Idc + Itrp + Iecs (1)

Among these currents, the discharge current Idc and the trapping current Itrp are currents that flow through the second conductive member 11V disposed on the inner surface of the casing 24. Further, as described above, the input current Iin to the discharge electrode 20 is controlled to be constant by the second current supply circuit 222. Therefore, the leakage current Iesc can be obtained by calculating the difference between the input current Iin and the sum of the two currents Idc and Itrp flowing through the second conductive member 11V (the following equation (2)).
Iesc = Iin− (Idc + Itrp) (2)

  The electric circuit unit 112 detects the difference between the input current Iin and the sum of the two currents Idc and Itrp flowing through the second conductive member 11V as the leakage current Iesc by the current difference measuring unit 230, and the detection result A signal based on this is output to the sensor control unit 111. Specifically, the electric circuit unit 112 detects the leakage current Iesc as follows.

  The current difference measurement unit 230 of the electric circuit unit 112 is electrically connected to the second conductive member 11V via the first shield line SL1 of the cable 120. In addition, the current difference measuring unit 230 is grounded via the exhaust gas pipe 415 or the chassis of the vehicle 500.

  In the second conductive member 11V, the reference potential is lower than the external reference potential by the amount of the leakage current Iesc that is insufficient with respect to the input current Iin. On the other hand, from the current difference measuring unit 230, the compensation current Ic flows through the first shield line SL1 so as to compensate for the decrease. The compensation current Ic is a current corresponding to the leakage current Iesc, and the current difference measurement unit 230 transmits the measurement value of the compensation current Ic to the sensor control unit 111 as the measurement value of the leakage current Iesc.

  The leakage current Iesc is a current having a correlation with the amount of the cation 80 used for charging the soot 82, and the amount of the cation 80 used for charging the soot 82 is the amount of the soot 82 in the exhaust gas. The corresponding amount. Therefore, the amount of soot 82 in the exhaust gas can be obtained by detecting (measuring) the leakage current Iesc. The sensor control unit 111 acquires the amount of soot 82 in the exhaust gas with respect to the leakage current Iesc detected by the current difference measurement unit 230 using a map or an arithmetic expression stored in advance.

  In this way, the sensor control unit 111 detects the amount of soot 82 in the exhaust gas by using the current change in the casing 24 of the particulate sensor 100 according to the amount of cations 80 captured. That is, the sensor control unit 111 detects the amount of soot 82 in the exhaust gas based on the amount of cations 80 captured by the particulate sensor 100.

  As described above, the particle sensor 100 of the present embodiment has the separation electrode 10 and the separation counter electrode 11 disposed on the inner surface of the insulating ceramic casing 24 so as to face each other (FIG. 3). ). Here, when the separation electrode 10 and the separation counter electrode 11 are arranged at positions away from the inner surface of the casing 24, it is necessary to form a sufficient space for arranging the electrodes 10 and 11 inside the casing 24. Or, it may be necessary to have a complicated structure so that each of the poles 10 and 11 and other members contact and do not short-circuit. According to the particle sensor 100 of the above embodiment, the separation electrode 10 and the separation counter electrode 11 are disposed on the inner surface of the insulating casing 24. More specifically, the separation electrode 10 is disposed on the inner surface of the casing 24 on the predetermined region (the inner surface of the first casing 27), while the inner surface of the casing 24 faces the inner surface of the opposing region facing the inner surface of the predetermined region. The separation counter electrode 11 is disposed on the inner surface of the second casing 29. Therefore, the structure of the particle sensor can be simplified as compared with the case where the poles 10 and 11 are arranged away from the inner surface of the casing 24. Further, the separation electrode 10 and the separation counter electrode 11 can be easily provided as constituent members of the particle sensor 100.

  Moreover, the casing 24 has the 1st casing 27 and the 2nd casing 29 which were divided | segmented by the predetermined plane containing the axis line CL direction (FIG. 5). Thereby, compared with the case where the casing 24 is integrally formed, the 1st and 2nd electroconductive member 10V, 11V can be arrange | positioned on the inner surface of the casing 24 easily.

  In addition, the separation unit 31 includes a narrow channel 31c having a channel cross-sectional area smaller than that of the mixing unit 71 in a part of the axis CL direction (FIG. 3). Further, the separation electrode 10 and the separation counter electrode 11 are arranged to face each other in the narrow channel 31c. Thereby, larger repulsive force and attractive force can be given to the floating cation 80 that passes through the narrow channel 31c. As a result, more floating cations 80 can be reliably moved to the separation counter electrode 11. That is, the floating cation 80 can be efficiently captured by the separation counter electrode 11, and the detection accuracy of the particle sensor 100 can be improved.

  The particulate sensor 100 is also disposed on the inner surface of the insulating casing 24 for the discharge electrode 20 (FIGS. 2 and 5). Therefore, the structure of the particle sensor 100 can be further simplified as compared with the case where the discharge electrode 20 is disposed away from the inner surface of the casing 24. Further, the discharge electrode 20 can be easily provided as a constituent member of the fine particle sensor 100.

  Further, the fine particle sensor 100 has a nozzle forming member 41 in which a nozzle opening 42 is formed (FIGS. 2 and 3). Thereby, it becomes possible to inject air to the mixing part 71 via the nozzle opening 42, and the mixing part 71 can be easily made into a negative pressure. Thereby, exhaust gas can be easily taken into the mixing part 71. The nozzle forming member 41 also functions as a discharge counter electrode 41. Thereby, the number of parts can be reduced as compared with the case where the discharge counter electrode 41 is separately provided, and the structure of the particle sensor 100 can be further simplified.

  The fine particle sensor 100 forms the first conductive member 10 </ b> V, the second conductive member 11 </ b> V, and the discharge electrode 20 by applying and baking a conductive paste on the inner surface of the casing 24. Thereby, each structural member 10V, 11V, and 20 can be arrange | positioned on the inner surface of the casing 24 easily.

B. Variations:
In addition, elements other than the elements described in the independent claims of the claims in the constituent elements in the above-described embodiments are additional elements and can be omitted as appropriate. Further, the present invention is not limited to the above-described examples and embodiments, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

B-1. First modification:
In the above embodiment, the first conductive member 10 </ b> V, the second conductive member 11 </ b> V, and the discharge electrode 20 are formed on the inner surface of the insulating casing 24 by applying and baking the conductive paste on the inner surface of the casing 24. Had been placed in. However, the arrangement method of the constituent members 10V, 11V, and 20 on the inner surface of the casing 24 is not limited to this. For example, the constituent members 10V, 11V, and 20 formed in advance in a predetermined shape may be disposed on the inner surface of the casing 24. This also simplifies the structure of the particle sensor 100 as in the above embodiment. Moreover, you may arrange | position at least 1 each component member 10V, 11V, 20 on the inner surface of the casing 24 using a conductive pace. Furthermore, the constituent members 10V, 11V, and 20 may be formed using a technique such as plating.

B-2. Second modification:
In the above embodiment, the casing 24 is divided into the first and second casings 27 and 29. However, the present invention is not limited to this. That is, the casing 24 may be integrally formed. Even in this case, the structure of the particle sensor 100 can be simplified by disposing the constituent members 10V, 11V, and 20 on the inner surface of the casing 24 as in the above embodiment.

B-3. Third modification:
In the above embodiment, the fine particle sensor 100 has the narrow channel 31c having a channel cross-sectional area smaller than that of the mixing unit 71, but is not limited thereto. That is, the relationship between the channel cross-sectional areas of the mixing unit 71 and the separation unit 31 can be set as appropriate. Even in this case, the structure of the particle sensor 100 can be simplified by disposing the constituent members 10V, 11V, and 20 on the inner surface of the casing 24 as in the above embodiment.

B-4. Fourth modification:
In the above-described embodiment, in order to supply high-pressure air to the nozzle opening 42, a gas supply channel 700 (for example, the air from the air supply unit 113 (FIG. 1B)) circulates in the casing 24 or the cable 120. The air supply pipe 123 shown in FIG. 3 and the through hole 308 shown in FIG. 4 are provided, but the present invention is not limited to this. That is, high-pressure air having an atmospheric pressure or higher may be supplied from the air supply unit 113 to the corona discharge unit 72 through the cable 120 or a pipe disposed outside the casing 24. Even in this case, similarly to the above-described embodiment, the mixing portion 71 can be set to a negative pressure by injecting the gas from the nozzle opening 42 toward the mixing portion 71.

B-5. Fifth modification:
In the above embodiment, the particle sensor 100 is used to detect the amount of soot in the exhaust gas discharged from the internal combustion engine. However, the particle sensor 100 can be used to detect particles in various gases. It can also be used for consumer applications other than vehicle applications.

B-6. Sixth modification:
In the above embodiment, positive ions are generated between the discharge electrode 20 and the nozzle forming member 41 by corona discharge, and repulsive force is generated between the positive electrode (mainly floating cations) at the separation electrode 10. Although configured, it is not limited to this. For example, by changing the positive and negative connection destinations of these members 10, 20, 41, negative ions are generated between the discharge electrode 20 and the nozzle forming member 41 by corona discharge, and the separation electrode 10 generates negative ions. A configuration in which repulsive force is generated between ions may be adopted to detect the amount of fine particles contained in the gas to be detected.

DESCRIPTION OF SYMBOLS 10 ... Electrode for isolation | separation 10V ... 1st electroconductive member 11 ... Counter electrode for isolation | separation 11V ... 2nd electroconductive member 14 ... 2nd protection member 14V ... Insulating member 20 ... Electrode for discharge 22 ... 1st outer cylinder 24 ... Casing 27 ... 1st casing 29 ... 2nd casing 31 ... Separation part 31a ... 1st flow path 31b ... 2nd flow path 31c ... Narrow flow path 35 ... Outflow hole 41 ... Nozzle formation member (for discharge) Counter electrode)
DESCRIPTION OF SYMBOLS 42 ... Nozzle opening 45 ... Inflow hole 64 ... Gasket 71 ... Mixing part 72 ... Corona discharge part 80 ... Cation 82 ... Soot 100 ... Fine particle sensor 100e ... Tip part 103 ... Joint part 104 ... Tool engaging part 110 ... Sensor drive part DESCRIPTION OF SYMBOLS 111 ... Sensor control part 112 ... Electric circuit part 113 ... Air supply part 120 ... Cable 123 ... Air supply pipe 130 ... Sensor system 132 ... Lead part 142 ... 1st protection member 152 ... Lead part 301,302,304 ... Terminal 308 ... through-hole 320 ... fixing member 324 ... lead wire 326 ... joint part 360 ... second outer cylinder 400 ... internal combustion engine 410 ... fuel supply part 411 ... fuel pipe 415 ... exhaust gas pipe 416 ... filter device 420 ... vehicle control part 500 ... Vehicle 700 ... Gas supply flow path CL ... Axis EW ... Electric wiring group

Claims (10)

In order to detect the amount of fine particles contained in the gas to be detected, the fine particles are charged using ions generated by corona discharge, and adsorbed ions that are ions used for charging and ions that are not used for charging. In the particle sensor that separates floating ions,
An insulating casing extending in the axial direction, an inflow hole for allowing the detection gas to flow into the inside, and one end side of the inflow hole for allowing the detection gas to flow out A casing having an outflow hole;
A corona discharge part formed in the casing and generating the ions by the corona discharge;
A mixing unit that is formed in the casing at a position closer to one end than the corona discharge unit, and mixes the ions and the fine particles flowing into the casing through the inflow hole;
A separation part that is formed in the casing and separates the adsorbed ions and the floating ions at a position closer to the one end than the mixing part;
The separation unit is
A separation electrode disposed on an inner surface of the casing, the separation electrode generating a repulsive force with the floating ions;
A separation counter electrode disposed on an inner surface of the casing opposite to the separation electrode, the separation counter electrode generating an attractive force with the floating ions. Fine particle sensor. The fine particle sensor according to claim 1,
The casing is
Having first and second casings respectively extending in the axial direction;
The separation electrode is disposed on the inner surface of the first casing,
The separation counter electrode is disposed on the inner surface of the second casing,
The casing is formed by adhering the first and second casings to each other in a state where the separation electrode and the separation counter electrode face each other. The fine particle sensor according to claim 1 or 2,
The separation part is a narrow flow path having a smaller cross-sectional area perpendicular to the axial direction than the mixing part, and has the narrow flow path in which the separation electrode and the separation counter electrode are respectively disposed on the inner surface. A fine particle sensor characterized by that. The fine particle sensor according to any one of claims 1 to 3,
The corona discharge part is
A discharge electrode disposed on the inner surface of the other end side at a position not overlapping with the separation electrode and the separation counter electrode, of the inner surface of the casing;
A fine particle sensor comprising: a discharge counter electrode that is a counter electrode of the discharge electrode, and that generates a corona discharge with the discharge electrode. The fine particle sensor according to claim 4, wherein
The inflow hole is formed in a portion of the casing that defines the mixing portion,
The particulate sensor further includes:
A conductive nozzle forming member that forms a nozzle opening that opens in the axial direction at a position between the discharge electrode and the mixing portion in the axial direction;
The fine particle sensor, wherein the nozzle forming member functions as the discharge counter electrode. The fine particle sensor according to claim 5, further comprising:
A gas supply flow path formed in the casing on the other end side of the nozzle opening, the gas supply flow for circulating an external gas blown from the other end side of the nozzle opening to the nozzle opening side A particle sensor characterized by having a path. The fine particle sensor according to any one of claims 1 to 6, further comprising:
A fine particle sensor comprising an insulating protective member disposed on the separation electrode and protecting the separation electrode. The fine particle sensor according to any one of claims 1 to 7,
At least one of the separation electrode and the separation counter electrode is formed by applying and baking a conductive paste on the inner surface of the casing. The fine particle sensor according to any one of claims 7 and 8, which is dependent on claim 4 to claim 6 and claim 4.
The fine particle sensor, wherein the discharge electrode is formed by applying and baking a conductive paste on an inner surface of the casing. The fine particle sensor according to any one of claims 1 to 9, further comprising:
A fine particle sensor comprising a protective outer cylinder surrounding an outer periphery of a portion of the casing exposed to the detected gas and having an opening for circulating the detected gas.

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