JP2014010099A - Fine particle sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fine particle sensor in which a sensor output is large, and an individual difference variation is small.SOLUTION: A fine particle sensor 1 for detecting fine particles S in gas to be measured EG circulating in a vent pipe EP includes: a space formation member 12 including an inlet 33I for taking in the gas to be measured EG and an outlet 43O for discharging taken-in gas EGI taken in from the inlet 33I, and constituting an internal space MX to which the taken-in gas EGI is introduced; an ion source 15 for generating ion CP by aerial discharge in the internal space MX; and a gas injection source 11 for injecting compressed air AK supplied from the outside via an injection hole 31N formed in itself to the internal space MX. The space formation member 12 is configured such that the taken-in gas EGI is introduced from the inlet 33I to the internal space MX by the compressed air AK injected via the injection hole 31N, and that the taken-in gas EGI and the ion CP are mixed.

Description

  The present invention relates to a fine particle sensor that is attached to a vent pipe and detects fine particles in a gas to be measured flowing through the vent pipe.

In an internal combustion engine (for example, a diesel engine or a gasoline engine), fine particles such as soot may be contained in the exhaust gas.
Exhaust gas containing such fine particles is purified by collecting the fine particles with a filter. Moreover, the particulates accumulated in the filter are burned and removed by raising the temperature of the filter as necessary. However, when a problem such as breakage of the filter occurs, unpurified exhaust gas is directly discharged downstream of the filter.
Therefore, there is a need for a particulate sensor capable of detecting particulates in exhaust gas in order to directly measure the amount of particulates in exhaust gas or detect a filter failure.

  For example, Patent Document 1 discloses a particle measurement processing method and apparatus. In Patent Document 1, gas containing ionized positive ion particles is mixed with exhaust gas containing fine particles taken into the channel from the exhaust pipe to charge the fine particles, and then discharged to the exhaust pipe. And the method of detecting the electric current (signal current) which flows according to the quantity of discharged | emitted charged fine particles and detecting the density | concentration of fine particles is disclosed.

WO2009 / 109688

By the way, in this fine particle sensor, ions are generated by air discharge of the ion source outside the internal space where the exhaust gas is introduced, and the generated ions are introduced into the internal space together with the compressed air through the injection holes of the gas injection source. It was jetting towards. Specifically, for example, the ion source includes a member with an injection hole that is set to a first potential, and a second potential that is disposed outside the internal space and is higher in potential than the first potential. In addition, an air discharge (corona discharge) between them causes ionization of N ₂ , O _2, etc. in the atmosphere to generate positive ions such as N ³⁺ , O ^2+, etc. Then, the generated ions are jetted together with the compressed air through the jet hole toward the internal space. The ions passing through the injection holes together with the compressed air are mixed with the exhaust gas introduced into the internal space to charge the fine particles, and then the charged fine particles are discharged together with the compressed air.

However, in the fine particle sensor having such a structure, most of the ions (N ³⁺ , O ²⁺ ) generated by the discharge do not pass through the injection hole and are applied to the member with the injection hole having the first potential described above. Collide and return to N ₂ , O _2, etc. Therefore, the number of ions that actually reach the fine particles in the exhaust gas through the injection holes is very small compared to ions generated by air discharge (corona discharge). For this reason, the amount of ions adhering to the fine particles is small, and as a result, the sensor output (for example, the magnitude of the signal current) is small. In addition, the amount of ions lost without passing through the injection hole easily changes due to individual differences in the sensor, such as the relative position of the injection hole and the discharge electrode, and the flow of air around the discharge electrode. Individual differences in the amount of ions reaching the fine particles also occurred, resulting in variations in individual differences in sensor output.

  The present invention has been made in view of such problems, and provides a fine particle sensor having a large sensor output and a small variation in individual differences.

  One aspect of the present invention for solving the above-described problem is a particulate sensor that is attached to a vent pipe and detects particulates in a gas to be measured that flows through the vent pipe, and includes an inlet for taking in the gas to be measured. And a space forming member that constitutes an internal space into which the intake gas is introduced, and that generates ions by air discharge in the internal space. An ion source, and a gas injection source that injects compressed air supplied from the outside toward the internal space through an injection hole formed therein, and the space forming member is compressed through the injection hole. The fine particle sensor is configured to introduce the intake gas from the intake into the internal space by air and mix the intake gas and the ions.

In this fine particle sensor, ions are generated in the internal space of the space forming member by the ion source. And the space formation member is comprised in the form which mixes the intake gas and ion which were led into the internal space from the inlet by the compressed air injected through the injection hole.
For this reason, many of the produced | generated ions can be mixed with intake gas. As a result, the fine particles in the intake gas can be made fine particles (hereinafter referred to as charged fine particles) charged with many ions attached thereto.
As a result, the amount of ions adhering to the fine particles, that is, the number of charged fine particles and the charge amount increase, and as a result, the sensor output (for example, the magnitude of the signal current) can be increased. In addition, since variations in the amount of ions that reach the fine particles due to differences in individual sensors are small, variations in sensor output among the individual sensors can be reduced.
Thus, a particle sensor having a large sensor output and a small variation in individual differences can be obtained.

  Examples of the air discharge type in the ion source include arc discharge and glow discharge in addition to corona discharge. In addition, as a form of an electrode that forms an ion source, for example, a space forming member that forms an internal space is used as one electrode, and a needle-like electrode disposed opposite to the electrode is used as the other electrode. Can be mentioned. Moreover, what adjoins on a board | substrate and arrange | positions two electrodes and produces the creeping discharge in the air between these is mentioned.

  In this particulate sensor, compressed air supplied from the outside is used as a gas injection source. As this compressed air, for example, a reciprocating compressor, a scroll compressor, and the like, as well as those generated by various pumps that generate and pump compressed air can be used.

  Furthermore, in the fine particle sensor described above, the ion source includes a needle electrode having a needle-like tip portion, and the tip portion of the needle-like electrode passes through the injection hole of the gas injection source. A fine particle sensor arranged on the axis of the hole may be used.

  In this sensor, the ion source includes a needle electrode having a needle tip. And the front-end | tip part of this acicular electrode is arrange | positioned on the axis line of the injection hole which passes along the injection hole of a gas injection source. Specifically, for example, a part in which the needle electrode is bent in the internal space so that the tip is positioned on the axis of the injection hole can be mentioned. As a result, ions are generated on the axis of the injection hole through which the compressed air is injected, so the generated ions are mixed with the intake gas more appropriately together with the compressed air to form fine particles in the intake gas. Ions can be attached, and a larger sensor output can be obtained.

  Further, in the fine particle sensor described above, the ion source includes a needle-like electrode having a needle-like tip portion, and a portion of the needle-like electrode located in the internal space excludes the tip portion. Thus, a fine particle sensor surrounded by an insulating member may be used.

  In this sensor, the ion source includes a needle electrode having a needle tip. As a result, even in the needle-like electrode, air discharge can be reliably generated at the tip portion, and ions can be generated efficiently. In addition, a portion of the needle electrode located in the internal space is surrounded by an insulating member except for the tip. For this reason, the insulation between the needle-like electrode and the space forming member can be kept high. Thus, the amount of ions generated can be stabilized, and the stability of the sensor output can be enhanced.

  Further, in the fine particle sensor described above, the space forming member has a collecting electrode for collecting floating ions that have not adhered to the fine particles among the ions, and is disposed in the internal space, A fine particle sensor provided with an auxiliary electrode for assisting the collection of the floating ions by the collection electrode may be used.

In this sensor, the space forming member includes a collecting electrode and an auxiliary electrode.
For this reason, floating ions can be reliably collected by the collection electrode, the sensor output can be accurately set to a value corresponding to the amount of fine particles, and the amount of fine particles can be detected more appropriately.

It is explanatory drawing explaining the state which applied the embodiment and applied the particulate detection system containing a particulate sensor to the exhaust pipe of the engine mounted in the vehicle. It is explanatory drawing which shows schematic structure of the fine particle detection system containing the fine particle sensor concerning embodiment. It is a longitudinal section showing the structure of the particulate sensor concerning an embodiment. It is sectional drawing which shows the structure of the fine particle sensor concerning embodiment, Comprising: It is a longitudinal cross-sectional view in the longitudinal cross section orthogonal to the cross section of FIG. It is explanatory drawing which illustrates typically the mode of taking in of fine particles, charge, and discharge in a fine particle charge part among fine particle sensors concerning an embodiment. It is a longitudinal cross-sectional view which shows the structure of the fine particle sensor concerning a deformation | transformation form.

(Embodiment)
A particle detection system 2 including a particle sensor 1 according to the present embodiment will be described with reference to the drawings. The particulate sensor 1 of this embodiment is mounted on an exhaust pipe EP of an engine ENG (internal combustion engine) mounted on the vehicle AM, and detects the amount of particulate S (soot) in the exhaust gas EG flowing through the exhaust pipe EP. (See FIG. 1). The particulate sensor 1 includes a detection unit 10 that contacts the exhaust gas EG. In addition to the particle sensor 1 including the detection unit 10, the particle detection system 2 is mainly configured by the cable 160, the circuit unit 201, and a pressure pump 300 that is a compressed air source that generates compressed air AK ( (See FIG. 2).
The detection unit 10 of the particulate sensor 1 is attached to an attachment part EPT in which an attachment opening EPO is perforated in the exhaust pipe EP (venting pipe). A part thereof (in FIG. 2, the right side (front end side) of the attachment portion EPT) is disposed in the exhaust pipe EP through the attachment opening EPO, and is in contact with the exhaust gas EG (measured gas).
The circuit unit 201 is connected to the detection unit 10 of the particle sensor 1 via a cable 160 made of a plurality of wiring members outside the exhaust pipe EP. The circuit unit 201 includes a circuit that drives the detection unit 10 and detects a signal current Is described later.

First, with reference to FIG. 2, the configuration on the electric circuit of the circuit unit 201 of the particle detection system 2 will be described. The circuit unit 201 includes a measurement control circuit 220, an ion source power circuit 210, and an auxiliary electrode power circuit 240.
Among these, the ion source power supply circuit 210 has a first output terminal 211 having a first potential PV1 and a second output terminal 212 having a second potential PV2. Specifically, the second potential PV2 is a positive high potential with respect to the first potential PV1. More specifically, the second output terminal 212 outputs a positive pulse voltage of 1 to 2 kV0-p obtained by half-wave rectifying a sine wave of about 100 kHz with respect to the first potential PV1. The ion source power supply circuit 210 constitutes a constant current power source that is feedback-controlled for its output current and autonomously maintains its effective value at a predetermined current value (for example, 5 μA).

  On the other hand, the auxiliary electrode power circuit 240 has an auxiliary first output terminal 241 that is electrically connected to the first output terminal 211 and is set to the first potential PV1, and an auxiliary second output terminal 242 that is set to the auxiliary electrode potential PV3. ing. Specifically, 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 (1 to 2 kV) of the second potential PV2, for example, DC 100 to 200 V The potential is

  Further, the signal current detection circuit 230 forming a part of the measurement control circuit 220 includes a signal input terminal 231 connected to the first output terminal 211 of the ion source power supply circuit 210 and a ground input terminal 232 connected to the ground potential PVE. Have. The signal current detection circuit 230 detects a signal current Is flowing between the signal input terminal 231 and the ground input terminal 232.

In addition, in the circuit unit 201, 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 first output terminal 211 of the ion source power circuit 210, the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240, and the signal input terminal 231 of the signal current detection circuit 230 are connected to the inner circuit case 250.
In the present embodiment, the inner circuit case 250 accommodates and surrounds the ion source power circuit 210, the auxiliary electrode power circuit 240, and the secondary iron core 271B of the insulation transformer 270, and the first potential wiring of the cable 160. 165 is conducting.

  On the other hand, the insulation transformer 270 has an iron core 271 wound around a primary iron core 271A wound around a primary coil 272 and a secondary iron core 271B wound around a power circuit coil 273 and an auxiliary electrode power supply coil 274. It is configured separately. 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 (the first output terminal 211 of the ion source power supply circuit 210).

Further, the measurement control circuit 220 including the ion source power supply circuit 210, the auxiliary electrode power supply circuit 240, the inner circuit case 250, and the signal current detection circuit 230 is connected to the ground input terminal 232 of the signal current detection circuit 230 and connected to the ground potential. It is surrounded by an outer circuit case 260 made of PVE. Further, in addition to the ground input terminal 232 of the signal current detection circuit 230, the primary iron core 271 </ b> A of the isolation transformer 270 is connected to the outer circuit case 260.
In this embodiment, the outer circuit case 260 includes the ion source power supply circuit 210, the auxiliary electrode power supply circuit 240, the inner circuit case 250, the measurement control circuit 220 including the signal current detection circuit 230, and the primary of the insulation transformer 270. The side iron core 271A is accommodated and surrounded, and is electrically connected to the ground potential wiring 167 of the cable 160.

The measurement control circuit 220 includes a regulator power source PS. The regulator power supply PS is driven by an external battery BT through the power supply wiring BC.
The measurement control circuit 220 includes a microprocessor 202 and can communicate with the control unit ECU that controls the internal combustion engine via the communication line CC. The measurement result (signal current Is) of the signal current detection circuit 230 described above. ), A value obtained by converting this into a fine particle amount, or a signal indicating whether or not the fine particle amount exceeds a predetermined amount can be transmitted to the control unit ECU. As a result, the control unit ECU can perform operations such as controlling the internal combustion engine and issuing a malfunction warning of a filter (not shown).

Part of the electric power input from the outside to the measurement control circuit 220 through the regulator power supply PS is distributed to the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 via the isolation transformer 270. The insulating transformer 270 forms a primary coil 272 that forms part of the measurement control circuit 220, a power circuit coil 273 that forms part of the ion source power circuit 210, and a part of the auxiliary electrode power circuit 240. The auxiliary electrode power supply side coil 274 and the iron core 271 (primary side iron core 271A, secondary side iron core 271B) are insulated from each other. For this reason, while electric power can be distributed from the measurement control circuit 220 to the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240, insulation between them can be maintained.
In the present embodiment, the insulating transformer 270 also serves as an auxiliary electrode insulating transformer that supplies power to the auxiliary electrode power supply circuit 240.

  The pressure feed pump 300 takes in the ambient air (air) around itself and is directed toward an ion gas injection source 11 described later through an air feed pipe 310 having tip portions inserted into the outer circuit case 260 and the inner circuit case 250. Then, clean compressed air AK is pumped.

  Next, the cable 160 will be described with reference to the longitudinal sectional views of FIGS. 3 and 4 in addition to FIG. 2. In the center portion of the cable 160, a second potential wiring 161 and an auxiliary potential wiring 162 made of copper wire, and a hollow air pipe 163 made of resin are arranged. The second potential wiring 161 and the auxiliary potential wiring 162 are covered with an insulating second potential wiring covering layer 164a and auxiliary potential wiring covering layer 164b made of resin, respectively. The radial periphery of the second potential wiring covering layer 164a (second potential wiring 161), the auxiliary potential wiring covering layer 164b (auxiliary potential wiring 162), and the air pipe 163 is surrounded by the inner insulator layer 164.

Further, the inner periphery of the inner insulator layer 164 is surrounded by a first potential wiring 165 made of a braided copper fine wire. In addition, an insulating insulator coating layer 166 made of resin is disposed around the first potential wiring 165 in the radial direction. Further, the circumference in the radial direction is covered with a ground potential wiring 167 made of a braided copper fine wire. An insulating outer insulating coating layer 168 made of resin is formed around the ground potential wiring 167 in the radial direction for protection.
In addition, the cable 160 can circulate gas in the longitudinal direction of the cable 160 through the gas flow passage 163H in the air pipe 163.

As described above, the circuit unit 201 is connected to the cable 160 (see FIG. 2). Specifically, the second output terminal 212 of the ion source power supply circuit 210 is set to the second potential PV2, and is connected to and connected to the second potential wiring 161. The auxiliary second output terminal 242 of the auxiliary electrode power circuit 240 is set to the auxiliary electrode potential PV3 and is connected to and connected to the auxiliary potential wiring 162. Furthermore, the first output terminal 211 of the ion source power supply circuit 210 is set to the first potential PV1, the auxiliary first output terminal 241 of the auxiliary electrode power circuit 240, the signal input terminal 231 of the signal current detection circuit 230, the inner circuit case 250, The first potential wiring 165 is connected and conductive. In addition, the ground input terminal 232 of the signal current detection circuit 230 is connected to and connected to the outer circuit case 260 and the ground potential wiring 167 to be the ground potential PVE.
In addition, the air supply pipe 310 communicates with the air pipe 163 of the cable 160 through the inner circuit case 250.

Next, the mechanical configuration of the particulate sensor 1 will be described with reference to the longitudinal sectional views of FIGS. 3 and 4, the upper side in the figure is the front end side, and the lower side in the figure is the base end side.
First, the detection unit 10 will be described. As described above, the detection unit 10 of the particulate sensor 1 is mounted on the mounting portion EPT having the mounting opening EPO in the exhaust pipe EP (venting pipe) of the engine ENG (internal combustion engine), and the exhaust gas EG (measured gas). To touch. The detection unit 10 is roughly composed of an ion source 15, a gas ejection source 11, a fine particle charging unit 12, a first conduction member 13, a needle electrode body 20, and an auxiliary electrode body 50 in terms of its electrical functions. .

A metal-made hollow cylindrical inner cylinder 80 is fitted on the distal end side of the cable 160, and a metal pipe holder 60 described later is fitted on the distal end side of the inner cylinder 80. . The inner cylinder 80 is externally fitted to the distal end side of the cable 160 and is caulked and connected to the first potential wiring 165 that covers the outer side in the radial direction of the inner insulator layer 164 of the cable 160. The wiring 165 is electrically connected to the first potential PV1.
As shown in FIG. 4, the air pipe 163 of the cable 160 has an end 163 </ b> S open in the inner cylinder 80. For this reason, the compressed air AK released from the air pipe 163 is further pumped from the inner cylinder 80 to the distal end side (upward in the drawing) through the ventilation through hole 61J drilled in the holding portion 61 of the pipe holder 60.

  Further, as shown in FIG. 3, the distal end side of the second potential wiring 161 of the cable 160 is exposed from the second potential wiring covering layer 164 a in the inner cylinder 80, and extends to the extension portion 21 of the needle electrode body 20. It is connected. The needle-like electrode body 20 is made of a tungsten wire, and has a substantially straight rod-like extension portion 21 and a needle-like tip portion 22 that is located at the tip portion (upper end portion in the drawing) and has a needle-like shape. It consists of. Further, the extension part 21 of the needle-like electrode body 20 is covered with a cylindrical needle-like electrode insulating pipe 75 made of an insulating ceramic such as alumina, and the needle-like electrode perforated in the holding part 61 of the pipe holder 60. It is inserted into the insertion hole 61 </ b> H and is held by the holding portion 61 together with the needle electrode insulating pipe 75.

  Further, the distal end side of the auxiliary potential wiring 162 of the cable 160 is exposed from the auxiliary potential wiring covering layer 164 b in the inner cylinder 80 and connected to the extending portion 51 of the auxiliary electrode body 50. The auxiliary electrode body 50 is made of a stainless steel wire, and includes an approximately straight rod-like extension portion 51, a bent-back portion 52 bent back in a U-shape on the tip side, and an auxiliary electrode portion 53 (auxiliary electrode). Become. It should be noted that the tip portion of the auxiliary electrode portion 53 is also shaped like a needle, which is a needle-like tip portion 53S. Further, the extended portion 51 of the auxiliary electrode body 50 is covered with a cylindrical auxiliary electrode insulating pipe 77 made of an insulating ceramic such as alumina, and the auxiliary electrode insertion hole 61 </ b> I is formed in the holding portion 61 of the pipe holder 60. The holding portion 61 is held together with the auxiliary electrode insulating pipe 77.

The pipe holder 60 shown in FIGS. 3 and 4 is made of stainless steel, and has a solid columnar holding portion 61, and a cylindrical cylindrical wall portion 63 extending from the periphery of the holding portion 61 to the tip side. Have Of these, the holding portion 61 has an annular holder flange portion 66 that bulges radially outward. In addition, the holding part 61 has a needle-like electrode insertion hole 61H, an auxiliary electrode insertion hole 61I, and a ventilation through-hole 61J extending in the vertical direction in the figure, and as described above, the needle-like electrode insertion hole The extension portion 21 of the needle electrode body 20 is inserted and held in 61H, and the extension portion 51 of the auxiliary electrode body 50 is inserted and held in the auxiliary electrode insertion hole 61I.
The pipe holder 60 is fitted and fixed to the inner cylinder 80 and is also electrically connected to a first potential PV1. The pipe holder 60 and the inner cylinder 80 form the first conductive member 13 that surrounds the extending portion 21 of the needle electrode body 20 and the extending portion 51 of the auxiliary electrode body 50.

Further, a bottomed cylindrical nozzle member 30, specifically, a nozzle portion 31 that forms the bottom thereof is fitted into the distal end side (upper side in the drawing) of the cylindrical wall portion 63 of the pipe holder 60. The nozzle member 30 is also made of stainless steel, and includes a nozzle portion 31 located at the bottom, and a cylindrical tube wall portion 33 extending from the periphery of the nozzle portion 31 to the tip side. Among these, the nozzle portion 31 has a concave shape whose center is directed toward the distal end side, and a fine through hole is formed at the center to form the nozzle 31N. On the other hand, the cylindrical wall portion 33 is perforated with an intake port 33I (see FIG. 4) (opened toward the downstream side of the exhaust pipe EP). As will be described later, the intake port 33I is an opening for taking the exhaust gas EG into a mixed region MX (described later) formed by the nozzle member 30 and the mixed discharge member 40.
In addition, the nozzle member 30 is fitted and fixed to the pipe holder 60, and is electrically connected to the first potential PV1.

  In addition, the nozzle part 31 of the nozzle member 30 is fitted into the distal end side of the cylindrical wall part 63 of the pipe holder 60, so that the pipe holder 60 (holding part 61, cylindrical wall part 63) and the nozzle part 31 of the nozzle member 30 An enclosed wall space DS is formed. Compressed air AK is supplied to the wall space DS through the ventilation through hole 61J of the holding portion 61 of the pipe holder 60. Further, the air AR originating from the compressed air AK is generated from the nozzle 31N of the nozzle portion 31. From this, it injects toward the mixing area | region MX of the front end side at high speed.

  Further, in the wall space DS, the extension part 21 of the needle electrode body 20 and the needle electrode insulation pipe 75 surrounding the extension part 21, the extension part 51 of the auxiliary electrode body 50 and the auxiliary electrode insulation pipe 77 surrounding the extension part 51 are provided. Projecting from the holding portion 61 of the pipe holder 60, and these extend through the nozzle portion 31 and further to the tip side (upward in the figure).

Among these, the needle-like tip portion 22 of the needle-like electrode body 20 penetrating the nozzle portion 31 is exposed from the needle-like electrode insulating pipe 75 in the mixed region MX. Further, the needle-like distal end portion 22 is disposed so as to face a facing surface 42T on the proximal end side of a collecting electrode 42 described later in the mixing region MX. For this reason, when a high voltage is applied between the needle-shaped tip 22 and the collecting electrode 42 (opposing surface 42T), air discharge occurs, ionizing N ₂ , O _{2 and the} like in the atmosphere, and positive ions ( For example, N ³⁺ , O ^{2+ (} hereinafter also referred to as ions CP) can be generated.
In addition, as shown in FIG. 4, the needle-like electrode body 20 passes through a position (a position away from the intake port 33 </ b> I) that is slightly radially outward from the axis AX of the nozzle 31 </ b> N in the nozzle portion 31. The needle-like tip 22 is exposed. That is, the needle-like tip portion 22 is disposed at a position shifted from the axis AX of the nozzle 31N.
On the other hand, the auxiliary electrode body 50 extends further to the tip side (upward in the drawing) than the needle-like electrode body 20.

A mixing / discharging member 40 is fitted on the distal end side (upper side in the drawing) of the cylindrical wall portion 33 of the nozzle member 30. The mixing and discharging member 40 is also made of stainless steel, and has a base end portion 41 located on the base end side (downward in the figure) and a cylindrical tip end side cylindrical wall portion extending from the periphery of the base end portion 41 to the tip end side. 43. Further, the distal end side of the distal end side cylinder wall portion 43 is closed by being covered with a lid member 48. Further, a discharge port 43O (opening toward the downstream side of the exhaust pipe EP) is formed in the distal end side cylindrical wall portion 43 at one location.
Of the mixed discharge member 40, the base end portion 41 is configured such that the inner space is narrowed in a slit shape by the collecting electrode 42 bulging inward. On the other hand, a cylindrical space is formed in the distal end side cylindrical wall portion 43. The collecting electrode 42 is formed with a notch 42K in accordance with the position of the inlet 33I of the nozzle member 30. Further, as described above, the opposed surface 42 </ b> T on the proximal end side of the collecting electrode 42 faces the needle-like distal end portion 22 of the needle-like electrode body 20.
The mixing / discharging member 40 is fitted and fixed to the nozzle member 30 and is electrically connected to a first potential PV1.

  Thus, in the nozzle member 30, the front end side surface 31 </ b> S facing upward in the drawing of the nozzle portion 31, the cylindrical wall portion 33, and the base end portion 41 (collecting electrode 42) of the mixed discharge member 40, a substantially cylindrical space. Is formed. This space forms a cylindrical mixed region MX1 in the mixed region MX described later. On the other hand, the slit-shaped internal space formed by the collecting electrode 42 at the base end portion 41 of the mixed discharge member 40 forms a slit-shaped mixed region MX2. Further, the cylindrical space in the distal end side cylinder wall portion 43 forms a discharge path EX communicating with the discharge port 43O. In addition, a lead-in path HK communicating from the intake port 33I to the mixing region MX (columnar mixing region MX1) is formed by the cutout portion 42K of the collecting electrode 42.

  Further, in the cylindrical mixing area MX1, air AR originating from the compressed air AK is injected at high speed from the nozzle 31N, and the injected air AR is injected into the cylindrical mixing area MX1, the slit-shaped mixing area MX2, and It is discharged from the discharge port 43O via the discharge path EX. Furthermore, since the atmospheric pressure in the cylindrical mixing region MX1 decreases due to the flow of the air AR injected at a high speed, the exhaust gas EG outside the intake port 33I passes through the intake passage HK from the intake port 33I and passes through the mixing region MX (circle). The columnar mixed region MX1 and the slit-shaped mixed region MX2) are incorporated. Further, in the cylindrical mixed region MX1, ions CP are generated by air discharge between the needle-shaped tip 22 and the facing surface 42T of the collecting electrode 42, so that the introduced intake exhaust gas EGI is The mixed space MX is mixed with the air AR containing the ions CP, and is discharged from the discharge port 43O via the discharge path EX together with the air AR.

  Further, the extension part 51 of the auxiliary electrode body 50 and the auxiliary electrode insulating pipe 77 surrounding the extension part 51 extend to the tip side (upward in the drawing) from the pipe holder 60 and the nozzle member 30 and bend back to the extension part 51. The part 52 is located in the front end side cylindrical wall part 43 of the mixed discharge member 40 (discharge path EX). And the auxiliary electrode part 53 which faces the base end side (downward in the figure) is located in the slit-shaped mixed region MX2 formed by the base end part 41 of the mixed discharge member 40.

  As shown in FIG. 3, a substantially cylindrical first insulating spacer 121 made of an insulating ceramic such as alumina is disposed on the distal end side (upper side in the drawing) of the holder flange portion 66 of the pipe holder 60. A substantially cylindrical second insulating spacer 122 made of an insulating ceramic such as alumina is also arranged on the base end side (lower side in the figure) of the holder flange portion 66. Further, a metal shell 90 made of stainless steel is disposed around these radial directions (in the horizontal direction in the figure).

The metal shell 90 includes a cylindrical portion 91 and a flange portion 95. Among these, the substantially cylindrical tubular portion 91 holds a holding hole 91 </ b> H that holds the pipe holder 60, the first insulating spacer 121, and the second insulating spacer 122 therein. Further, the base end side of the cylindrical portion 91 is a female screw portion 92 having a female screw formed on the inner wall.
On the other hand, the flange portion 95 is a plate shape projecting radially outward from the distal end portion of the cylindrical portion 91 and has a substantially oval outer shape. Moreover, it has the bolt through-holes 95H and 95H penetrated in own thickness direction (2 places in this embodiment).

Further, the plug fitting 100 is screwed to the female threaded portion 92 of the cylindrical portion 91 of the metal shell 90 with a male threaded portion 102 having a male thread formed on the outer periphery thereof. The stopper metal 100 has a substantially cylindrical shape and surrounds the inner cylinder 80 in a non-contact manner. Further, the plug fitting 100 has a distal end pressing portion 101 having a flat distal end surface 101S formed on the distal end side (upward in the drawing) of the male screw portion 102 and having a smaller diameter than the male screw portion 102. Further, on the base end side (downward in the drawing) from the male screw portion 102, there is a hexagonal portion 103 that protrudes in a flange shape toward the outer side in the radial direction and has a hexagonal outer periphery.
When the male thread portion 102 of the stopper fitting 100 is screwed into the female thread portion 92 of the metal shell 90, the stopper fitting 100 advances to the distal end side, and the distal end pressing portion 101 presses the second insulating spacer 122 toward the distal end side. Then, this 2nd insulation spacer 122 presses the holder flange part 66 of the pipe holder 60 toward the front end side. Further, the holder flange portion 66 presses the first insulating spacer 121 toward the distal end side. The first insulating spacer 121 is engaged with the holding hole 91 </ b> H of the cylindrical portion 91 of the metal shell 90 through the plate packing 124. Thereby, the pipe holder 60, the 1st insulating spacer 121, the 2nd insulating spacer 122, the plate packing 124, and the stopper metal fitting 100 are hold | maintained at the metal fitting 90, and are integrated.
In addition, a first insulating spacer 121 and a second insulating spacer 122 are interposed between the pipe holder 60 and the metal shell 90 so as to separate and insulate them from each other. Of the pipe holder 60, the holder flange portion 66 projecting outward in the radial direction and the metal shell 90 (cylindrical portion 91) are spaced apart from each other to maintain insulation therebetween. Yes. Further, the first insulating spacer 121 is interposed between the cylindrical wall portion 63 of the pipe holder 60 and the exhaust pipe EP in a state where the detection unit 10 is mounted on the exhaust pipe EP to separate and insulate the two. Yes.

As shown in FIG. 4, when the detection unit 10 is attached, the nozzle member 30, the mixed discharge member 40, and the like are inserted into the exhaust pipe EP from the attachment opening EPO of the attachment part EPT in the exhaust pipe EP. The stud bolts EPB and EPB provided adjacent to the mounting opening EPO are respectively inserted into the bolt through holes 95H of the flange portion 95 and fastened with nuts EPN. Thereby, the detection part 10 including the metal shell 90 is fixed to the attachment part EPT of the exhaust pipe EP.
An annular gasket holding groove 96 is formed around the holding hole 91H in the front end side surface 90S of the metal shell 90, and the mounting portion EPT of the exhaust pipe EP and the metal shell 90 are held by this gasket holding. They are hermetically coupled through a copper gasket 130 disposed in the groove 96.
Thereby, the gasket 130, the metal shell 90, and the stopper metal 100 are set to the same ground potential PVE as that of the exhaust pipe EP.

Furthermore, a cylindrical outer cylinder 110 made of stainless steel is connected to the base end portion 104 of the stopper fitting 100. The outer cylinder 110 surrounds the inner cylinder 80 and the distal end portion 160 </ b> S of the cable 160 from the outside in the radial direction, and the distal end portion 110 </ b> S is laser-welded to the base end portion 104 of the plug fitting 100 over the entire circumference.
In addition, the base end portion 110 </ b> K of the outer cylinder 110 is fixed to the cable 160 by caulking, with the outer shape being reduced in diameter from the distal end side. At the same time, the caulking portion 110KK of the base end portion 110K of the outer cylinder 110 passes through the outermost outer insulating coating layer 168 of the cable 160 and is electrically connected to the ground potential wiring 167 therein. Thus, both the outer cylinder 110 and the ground potential wiring 167 are set to the ground potential PVE, like the exhaust pipe EP, through the metal shell 90, the plug fitting 100, and the gasket 130 made of metal.
In the present embodiment, in order to prevent the front end portion 160S of the cable 160 from swinging in the outer cylinder 110, a cylindrical shape is formed between the front end portion 160S of the cable 160 and the outer cylinder 110 from insulating rubber. A grommet 125 is interposed.

Next, the electrical functions and operations of each part of the particle sensor 1 of the present embodiment will be described with reference to FIG. 5 in addition to FIGS. FIG. 5 schematically shows the electrical function and operation of the detection unit 10 of the particle sensor 1 for easy understanding, and there are parts different from the forms described in other figures. Please note that.
The acicular electrode body 20 is connected to and electrically connected to the second output end 212 of the ion source power supply circuit 210 via the second potential wiring 161 of the cable 160. Therefore, as described above, the needle-like electrode body 20 is set to the second potential PV2, which is a positive half-wave rectified pulse voltage of 100 kHz and 1 to 2 kV0-p with respect to the first potential PV1.
Further, the auxiliary electrode body 50 is connected to and connected to the auxiliary second output terminal 242 of the auxiliary electrode power circuit 240 via the auxiliary potential wiring 162 of the cable 160. Accordingly, as described above, the auxiliary electrode body 50 is set to the auxiliary electrode potential PV3 that is a positive DC potential of 100 to 200 V with respect to the first potential PV1.
Further, the inner cylinder 80, the pipe holder 60, the nozzle member 30, and the mixing and discharging member 40 are connected to the first output terminal 211 of the ion source power supply circuit 210 and the auxiliary electrode power supply circuit 240 via the first potential wiring 165 of the cable 160. The auxiliary first output terminal 241, the inner circuit case 250 surrounding these circuits, and the signal input terminal 231 of the signal current detection circuit 230 are connected and conductive. These are set to the first potential PV1.
In addition, the outer cylinder 110, the plug fitting 100, the metal fitting 90, and the gasket 130 are connected to the outer circuit case 260 and the signal surrounding the measurement control circuit 220 including the signal current detection circuit 230 via the ground potential wiring 167 of the cable 160. The current detection circuit 230 is connected to and connected to the ground input terminal 232. These are set to the same ground potential PVE as the exhaust pipe EP.

Therefore, as described above, in the mixing region MX, the opposing surface 42T of the collecting electrode 42 of the mixed discharge member 40 that is set to the first potential PV1 and the second potential PV2 that is a positive potential higher than this. Air discharge, specifically, corona discharge occurs between the needle-shaped tip 22. More specifically, a positive needle corona PC in which a corona is generated around the needle-like tip 22 serving as the positive electrode is generated. As a result, N, O, etc. of the atmosphere (air) forming the atmosphere is ionized, and positive ions CP are generated. In addition, compressed air AK (air AR) is injected into the mixing region MX from the intra-wall space DS through the nozzle 31N.
In the present embodiment, the needle-like tip 22 (tip) of the needle-like electrode body 20 (needle-like electrode) and the facing surface 42T of the collecting electrode 42 correspond to the ion source 15. Moreover, the pipe holder 60 (holding part 61, cylinder wall part 63) and the nozzle part 31 of the nozzle member 30 surrounding the inner space DS form the gas injection source 11, and the nozzle 31N corresponds to the injection hole.

When the air AR is injected into the mixing region MX (cylindrical mixing region MX1), as described above, the atmospheric pressure of the cylindrical mixing region MX1 decreases, so that the exhaust gas EG passes through the intake passage HK through the intake passage HK. It is taken into the mixing area MX (cylindrical mixing area MX1, slit-shaped mixing area MX2). The intake exhaust gas EGI is mixed with the air AR, and is discharged from the discharge port 43O via the discharge path EX together with the air AR.
At this time, if the exhaust gas EG contains fine particles S such as soot, the fine particles S are also taken into the mixing region MX as shown in FIG. By the way, the injected air AR is mixed with ions CP generated in the mixing region MX. For this reason, the fine particles S such as soot that are taken in are attached to the ions CP to become positively charged fine particles SC, and in this state, the air passes through the mixing region MX and the discharge path EX, and is discharged from the discharge port 43O. It is discharged together with AR.
On the other hand, among the ions CP generated in the mixed region MX and injected by being mixed with the air AR, the floating ions CPF that have not adhered to the fine particles S are generated from the auxiliary electrode portion 53 (auxiliary electrode) of the auxiliary electrode body 50. It receives repulsive force and adheres to each part of the mixed discharge member 40 (base end part 41, front end side cylinder wall part 43) forming the collecting electrode 42 having the first potential PV1, and is not discharged (captured).

Therefore, the signal current Is corresponding to the charge amount of the discharged ions CPH discharged by the charged fine particles SC is detected by the signal current detection circuit 230, whereby the amount of the fine particles S in the exhaust gas EG can be detected.
In the present embodiment, the fine particle charging portion 12 is formed by the nozzle member 30, the mixing discharge member 40, and the lid member 48 that form the mixing region MX and the collecting electrode 42, and the fine particle charging portion 12 corresponds to a space forming member. . Further, the mixing area MX (columnar mixing area MX1, slit-shaped mixing area MX2) and the discharge path EX correspond to the internal space.

As described above, in the particle sensor 1 of the present embodiment, the particle charging unit 12 (space formation) is performed by the ion source 15 (the needle-like tip portion 22 of the needle-like electrode body 20 and the opposing surface 42T of the collection electrode 42). The ions CP are generated in the mixed region MX (internal space) of the member. The fine particle charging unit 12 is connected to the intake exhaust gas EGI (intake gas) introduced from the intake port 33I into the mixing region MX by the compressed air AK (air AR) injected through the nozzle 31N (injection hole). Ion CP is mixed, and the ion CP is adhered to the fine particles S in the intake exhaust gas EGI to form charged fine particles SC. The charged fine particles are discharged from the outlet 43O together with the compressed air AK (air AR) and the intake exhaust gas EGI. It is comprised in the form which discharges SC.
For this reason, ions CP are generated outside the mixing region MX (internal space), and the generated ions CP are injected into the mixing region MX through the nozzle 31N (injection hole) together with the compressed air AK (air AR). Compared with the above-described method, a large amount of the generated ions CP are mixed with the intake exhaust gas EGI, and the fine particles S in the intake exhaust gas EGI are charged with the charged fine particles SC that are charged with many ions CP attached thereto. can do.
As a result, the amount of ions CP adhering to the fine particles S, that is, the number of charged fine particles SC and the amount of charge increase, and as a result, the sensor output (for example, the magnitude of the signal current) can be increased. In addition, since fluctuations in the amount of ions CP reaching the fine particles S due to differences in individual sensors are also reduced, variations in sensor output among individual sensors can be reduced.
Thus, a particle sensor having a large sensor output and a small variation in individual differences can be obtained.

  Furthermore, in the fine particle sensor 1 of the present embodiment, the ion source 15 includes a needle-like electrode (needle-like electrode body 20) having a needle-like tip (needle-like tip 22). Thereby, in the needle electrode body 20, the air discharge (corona discharge) is reliably generated at the needle tip portion 22 at the tip thereof, and the ions CP can be efficiently generated. In addition, a portion of the needle electrode body 20 located in the mixed region MX (internal space) is surrounded by a needle electrode insulating pipe 75 (insulating member) in the radial direction except for the needle-like tip 22. ing. For this reason, the insulation between the needle electrode body 20 and the fine particle charging portion 12 (space forming member) can be kept high. Thus, the amount of ions CP generated can be stabilized, and the stability of the sensor output can be improved.

Furthermore, in the particle sensor 1 of the present embodiment, the particle charging unit 12 (space forming member) has a collection electrode 42 for collecting the floating ions CPF that have not adhered to the particles S among the ions CP. , An auxiliary electrode (auxiliary electrode portion 53 of the auxiliary electrode body 50) for assisting the collection of the floating ions CPF by the collecting electrode 42 is provided.
Therefore, the floating ions CPF can be reliably collected by the collection electrode 42, the sensor output can be accurately set to a value corresponding to the amount of the fine particles S, and the amount of the fine particles S can be detected more appropriately. it can.

(Deformation)
Next, a modification of the above-described embodiment will be described with reference to FIG. In the fine particle sensor 1 of the above-described embodiment, the needle-like tip portion 22 of the needle-like electrode body 20 is disposed at a position slightly deviated radially outward from the axis AX of the nozzle 31N in the mixed region MX of the fine particle charging unit 12. (See FIG. 4).

  On the other hand, in the fine particle sensor 1A of the present modified embodiment, as shown in FIG. 6, the needle-like electrode body 20 is positioned slightly out of the nozzle portion 31 radially outward from the axis AX of the nozzle 31N (intake port). In the mixed region MX, the extending portion 21 is exposed from the needle electrode insulating pipe 75 and bent inward in the radial direction. Thereby, the needle-like tip portion 22 of the needle-like electrode body 20 is disposed on the axis AX passing through the nozzle 31N (injection hole). In addition, about another structure, it is the same as that of the fine particle sensor 1 of embodiment.

  Thereby, the fine particle sensor 1 </ b> A of the present modified embodiment has the same effects as the embodiment. In addition, in the fine particle sensor 1A of the present modified embodiment, the needle-like tip portion 22 of the needle-like electrode body 20 is disposed on the axis AX of the nozzle 31N passing through the nozzle 31N (injection hole). As a result, the ions CP are generated on the axis AX of the nozzle 31N from which the compressed air AK (air AR) is injected, so that the generated ions CP are more appropriately taken together with the compressed air AK (air AR). By mixing with the exhaust gas EGI, the ions CP can be adhered to the fine particles S in the intake exhaust gas EGI, and a larger sensor output can be obtained.

In the above, the present invention has been described based on the fine particle sensor 1 of the embodiment and the modified fine particle sensor 1A. However, the present invention is not limited to the embodiment and the modified embodiment, and does not depart from the gist of the present invention. Needless to say, the present invention can be appropriately changed and applied.
For example, in the embodiment and the modification, the example in which the detection unit 10 of the particle sensor 1 or 1A is connected to the circuit unit 201 of the particle detection system 2 via the cable 160 is shown. The form can be changed as appropriate, for example, the part 10 and the circuit part 201 are connected (integrated).
In the embodiment and the modified embodiment, the needle electrode body 20 and the auxiliary electrode body 50 extend in a straight bar shape and penetrate the nozzle portion 31. However, the needle electrode body 20 and the auxiliary electrode body 50 are in a form. Can be appropriately changed.
In the embodiment and the modification, the ion source 15 is configured by the needle-like tip portion 22 of the needle-like electrode body 20 and the facing surface 42T of the collecting electrode 42. However, the form of the electrode that forms the ion source 15 is as follows. Changes can be made as appropriate.
Furthermore, in the embodiment and the modified embodiment, a portion of the needle-like electrode body 20 located in the mixed region MX (internal space) is removed by the cylindrical needle-like electrode insulating pipe 75 except for the needle-like tip portion 22. Besieged. However, instead of this, for example, a needle electrode body surrounded by a sheet-like insulating plate can be used.

EP exhaust pipe (venting pipe)
EPO mounting opening EG Exhaust gas (measured gas)
EGI Intake exhaust gas (intake gas)
S Fine particle SC Charged fine particle CP Ion CPF Floating ion CPH Discharged ion Is Signal current 1, 1A Fine particle sensor 2 Fine particle detection system 10 Detection unit 11 Gas injection source DS Wall space 12 Fine particle charging unit (space forming member)
15 Ion source 20 Needle-like electrode body 22 Needle-like tip (of ion-like electrode body) (ion source)
30 Nozzle member (particulate charging part)
31 Nozzle (Particle Charger)
31N Nozzle 33I Intake PV1 First potential PV2 Second potential PV3 Auxiliary electrode potential PVE Ground potential 40 Mixing discharge member (particulate charging part)
MX mixing area (internal space)
MX1 Cylindrical mixing area (internal space)
MX2 Slit-shaped mixing area (internal space)
EX discharge path (internal space)
HK lead-in path 42 collection electrode 42T (collection electrode) facing surface (ion source)
43O Discharge port 48 Lid member (Particle charging part)
50 Auxiliary electrode body 53 Auxiliary electrode part (auxiliary electrode)
75 Needle-shaped electrode insulation pipe (insulation member)
AK compressed air (gas)
AR Air (gas)
201 Circuit Unit 210 Ion Source Power Supply Circuit 220 Measurement Control Circuit 230 Signal Current Detection Circuit 240 Auxiliary Electrode Power Supply Circuit

Claims (4)

A fine particle sensor that is mounted on a ventilation pipe and detects fine particles in a gas to be measured flowing through the ventilation pipe,
A space forming member that includes an intake port for taking in the gas to be measured, and an exhaust port for discharging the intake gas taken in from the intake port, and constitutes an internal space into which the intake gas is introduced;
An ion source that generates ions by air discharge in the internal space;
A gas injection source for injecting compressed air supplied from outside toward the internal space through an injection hole formed in the device;
The space forming member is
A fine particle sensor configured to introduce the intake gas from the intake into the internal space by the compressed air injected through the injection hole, and mix the intake gas and the ions. The fine particle sensor according to claim 1,
The ion source is
Including a needle-like electrode having a needle-like tip,
The fine particle sensor, wherein the tip of the needle electrode is disposed on an axis of the injection hole passing through the injection hole of the gas injection source. The fine particle sensor according to claim 1 or 2,
The ion source is
Including a needle-like electrode having a needle-like tip,
Of the needle-like electrode, the part located in the internal space is
A fine particle sensor surrounded by an insulating member except for the tip. The fine particle sensor according to any one of claims 1 to 3,
The space forming member is
Having a collecting electrode for collecting floating ions not attached to the fine particles among the ions;
A fine particle sensor provided with an auxiliary electrode disposed in the internal space and assisting in collecting the floating ions by the collecting electrode.

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