JP6596386B2 - Particle detection system - Google Patents

Description

  The present invention relates to a fine particle detection system including a sensor main body portion that is attached to a vent pipe and detects the amount of fine particles in a gas to be measured flowing through the vent pipe.

  2. Description of the Related Art There is known a fine particle detection system including a sensor main body portion that is used by being attached to a metal ventilation pipe having a ground potential and detects the amount of fine particles contained in a gas to be measured flowing through the ventilation pipe. For example, there is a particulate detection system that is mounted on an exhaust pipe of an internal combustion engine (diesel engine, gasoline engine, etc.) and includes a sensor main body that detects the amount of particulates such as soot contained in exhaust gas. In this particulate detection system, the exhaust gas flowing through the exhaust pipe is taken in, the ions generated in the ion source are attached to the particulates contained in the exhaust gas to form charged particulates, and then discharged into the exhaust pipe together with the introduced exhaust gas To do. On the other hand, floating ions that have not adhered to the fine particles among the ions generated by the ion source are collected. Then, a current value corresponding to the difference between the amount of ions generated by the ion source and the amount of trapped floating ions is measured, and the amount of fine particles contained in the gas to be measured is measured. For example, Patent Document 1 discloses such a particle detection system (see FIGS. 2 to 6 and the like of Patent Document 1).

  In the particulate detection system of Patent Document 1, four cables extend from the sensor main body. Two of these cables are a triple coaxial cable (triaxial cable), that is, a central conductor, a cylindrical inner conductor disposed coaxially on the radially outer side of the central conductor, and a radially outer side of the inner conductor. And a cylindrical outer conductor disposed coaxially with each other. On the other hand, the remaining two are single-core cables that conduct to the heater.

Of the two triple coaxial cables, the center conductor of one of the triple coaxial cables is set to the second potential and is conducted to the discharge electrode of the ion source. Further, the inner conductor is set to the first potential and is conducted to the first potential fitting, and the outer conductor is conducted to the mounting fitting attached to the vent pipe having the ground potential. As a result, the center conductor set to the second potential is double-shielded, and the inner conductor set to the first potential is also surrounded by the outer conductor and shielded.
The center conductor of the other triple coaxial cable is set to a third potential, and an auxiliary electrode (third potential) that assists in collecting floating ions that have not adhered to the fine particles among the generated ions to the first potential fitting. Conductive to the bracket). Further, like the one of the triple coaxial cables, the inner conductor is set to the first potential and is conducted to the first potential fitting, and the outer conductor is conducted to the mounting fitting that is set to the ground potential. Thereby, the center conductor set to the third potential is double shielded, and the inner conductor set to the first potential is also shielded by the outer conductor.

JP2015-129712A

  However, when a triple coaxial cable is used in the particle detection system as in Patent Document 1, the triple coaxial cable itself is expensive, and the cost of the particle detection system increases. In addition, the triple coaxial cable takes time for strip processing for exposing the center conductor, the inner conductor, and the outer conductor, respectively, and this also costs. In addition, since the three conductors of the center coaxial cable, the inner conductor, and the outer conductor of the triple coaxial cable are connected to the respective members in the sensor main body, high positional accuracy is required for assembly, and costs are increased. Thus, the triple coaxial cable has an advantage that the shielding of the center conductor and the inner conductor is easy, but the cost is high.

  The present invention has been made in view of such a situation, and without using a triple coaxial cable, a central conductor that is set to the second potential and conducted to the discharge electrode, and a first potential that is conducted to the first potential fitting. An object of the present invention is to provide a particle detection system that can shield a conductor to be performed and that can reduce the particle detection system at a low cost.

  One aspect of the present invention for solving the above-described problems is a sensor main body portion that is attached to a vent pipe having a ground potential and detects the amount of fine particles in a gas to be measured that circulates in the vent pipe, and a circuit section. The sensor main body includes a mounting bracket that is mounted on the vent pipe and has a ground potential, a first potential bracket that has a first potential different from the ground potential, a ground potential, and A discharge electrode which generates a second electric potential different from the first electric potential and generates ions to be attached to the fine particles by an air discharge generated between the first electric potential fitting and the fine particle detection system. A first central conductor that is set to the second potential and is connected to the discharge electrode; a first inner insulating layer that covers a circumference of the first center conductor in a radial direction; and is connected to the first potential bracket that is set to the first potential; Radial circumference of the first inner insulating layer Having a first outer conductor disposed coaxially with the first central conductor, and a first outer insulating layer covering the periphery of the first outer conductor in the radial direction, and extending from the sensor main body portion to the circuit portion. The first coaxial cable is connected to the mounting bracket to be grounded, and is separated from the first coaxial cable and extends from the sensor main body to the circuit portion. The diameter of the first coaxial cable A fine particle detection system comprising a braided tube that surrounds the outer side in the direction and is made of a fine metal wire.

The fine particle detection system includes the first coaxial cable and a braided tube that surrounds the radially outer side. Therefore, the first central conductor that is set to the second potential and is connected to the discharge electrode is connected to the first outer conductor and the braided tube. In addition to being surrounded and double-shielded, the first outer conductor that is set to the first potential and is conducted to the first potential fitting is also surrounded by the braided tube and shielded.
Furthermore, since the first coaxial cable and the braided tube are separate, unlike the case where a triple coaxial cable is used, the connection of the first center conductor and the first outer conductor to the sensor body and the sensor body of the braided tube The connection to the unit can be performed independently. For this reason, the assembly of the first coaxial cable and the braided tube becomes easier than when a triple coaxial cable is used, and the cost can be reduced. Therefore, the particle detection system can be made inexpensive.

As the “braided tube”, for example, a braided tube knitted with stainless steel wire, a braided tube knitted with iron wire with nickel plating on the surface, a braided tube knitted with copper wire with silver plating on the surface, etc. Can be mentioned.
As the “first outer conductor” of the first coaxial cable and the “second outer conductor” of the second coaxial cable described later, for example, an outer conductor made of a braided tube knitted with copper wire or a strip-shaped metal foil can be used without any gaps. Examples thereof include an outer conductor that is spirally wound into a cylindrical shape, and an outer conductor that is formed of a composite in which a strip-shaped metal foil is spirally wound around the radial direction of the braided tube without any gap.

  Further, in the fine particle detection system described above, the sensor body is set to a third potential different from a ground potential, the first potential, and the second potential, and adheres to the fine particles among the generated ions. A third potential fitting that assists in collecting the floating ions that are not present in the first potential fitting, and the fine particle detection system includes the second central conductor that is set to the third potential and is conducted to the third potential fitting, A second inner insulating layer covering the periphery of the second central conductor in the radial direction, the first potential being made conductive to the first potential fitting, and coaxial with the second central conductor around the radial direction of the second inner insulating layer And a second outer insulating layer that covers the circumference of the second outer conductor in the radial direction, extends from the sensor main body portion to the circuit portion, and passes through the braided tube. Particulate detection with second coaxial cable It may be a stem.

In the above-described particulate detection system, the second coaxial cable passing through the braided tube is provided, so that the second central conductor that is set to the third potential and is connected to the third potential fitting is surrounded by the second outer conductor and the braided tube. In addition to being shielded twice, the second outer conductor that is set to the first potential and is conducted to the first potential fitting is also surrounded by the braided tube and shielded.
Furthermore, since the second coaxial cable and the braided tube are separate, unlike the case of using a triple coaxial cable, the connection of the second center conductor and the second outer conductor to the sensor body and the sensor body of the braided tube The connection to the unit can be performed independently. For this reason, the assembly of the second coaxial cable and the braided tube becomes easier than when a triple coaxial cable is used, and the cost can be reduced. Therefore, the particle detection system can be made inexpensive.

  Furthermore, in the particulate detection system according to any one of the above, the sensor body includes a heater that generates heat when energized, and the particulate detection system is electrically connected to the heater, and the circuit is connected to the circuit from the sensor body. A fine particle detection system including a pair of heater energization wires extending to the section and passing through the braided tube may be used.

  The fine particle detection system described above includes a pair of heater energization wires that conduct to the heater, and these heater energization wires are also arranged in the braided tube. For this reason, since these heater energization wires and the first coaxial cable (including the second coaxial cable when the second coaxial cable is included) can be collectively handled by the braided tube, the particle detection system can be easily handled.

As the “heater”, for example, when the sensor body has a plate-like sensor element made of an insulator and forming an ion source, the sensor element is built in the sensor element, and the sensor element is heated to form a sensor element. A heater that removes adhering soot and the like can be used.
In the case where the sensor main body has an inner metal fitting that is set to the first potential on the inner side in the radial direction of the mounting metal fitting that is set to the ground potential, and an insulating spacer that insulates both of the mounting metal fitting and the inner metal fitting. A heater that is built in the insulating spacer and heats the insulating spacer to remove soot and the like attached to the insulating spacer.

Further, when the sensor main body has a rod-shaped needle-shaped electrode body that forms a discharge electrode and an insulating pipe that covers the circumference of the needle-shaped electrode body in the radial direction, the needle-shaped electrode body is provided on the insulating pipe. A heater for heating may be mentioned.
Further, when the sensor main body has a rod-shaped auxiliary electrode body that forms the third potential metal fitting and an insulating pipe that covers the circumference of the auxiliary electrode body in the radial direction, the auxiliary electrode body is provided for heating the auxiliary electrode body. The heater which performs is mentioned.

It is explanatory drawing which shows the whole particulate detection system of the state which concerns on embodiment and with which the sensor main-body part was mounted | worn with the exhaust pipe. It is a longitudinal section of a sensor main part and a cable among particulate detection systems concerning an embodiment. It is a longitudinal cross-sectional view about the longitudinal cross section orthogonal to FIG. 2 of a sensor main-body part and a cable among the fine particle detection systems which concern on embodiment. It is an exploded perspective view of a sensor main part and a cable among particulate detection systems concerning an embodiment. It is explanatory drawing which shows typically the mode of taking in of the microparticles | fine-particles in the sensor main body part which concerns on embodiment, charging, and discharge | emission. It is a longitudinal section of a sensor main part and a cable among particulate detection systems concerning a modification. It is a longitudinal cross-sectional view about the longitudinal cross section orthogonal to FIG. 6 of a sensor main-body part and a cable among the microparticle detection systems which concern on a deformation | transformation form. It is an exploded perspective view of a sensor main part and a cable among particulate detection systems concerning a modification.

(Embodiment)
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the entire particulate detection system 1 in a state where the sensor body 5 is mounted on an exhaust pipe (vent pipe) EP. 2 and 3 are longitudinal sectional views of the sensor main body 5 and the like in the particulate detection system 1, and FIG. 4 is an exploded perspective view of the sensor main body 5 and the like. FIG. 5 schematically shows how the fine particles S are taken in, charged and discharged in the sensor body 5. Of the sensor body 5 in the axial direction GH (vertical direction in FIGS. 2, 3 and 5), the side (downward in FIGS. 2, 3 and 5) attached to the exhaust pipe EP is the tip. The side (outside in FIG. 2, FIG. 3 and FIG. 5) arranged outside the side GS and the exhaust pipe EP is defined as the rear end side GK.

  The fine particle detection system 1 is a sensor that detects the amount of fine particles S such as soot contained in a gas to be measured EG such as exhaust gas flowing in the exhaust pipe EP of the internal combustion engine (engine) ENG (FIGS. 1 and FIG. 1). 5). This fine particle detection system 1 (see FIGS. 1 to 4) includes a sensor main body portion 5, a circuit portion 110, a first coaxial cable 70 extending from the sensor main body portion 5 to the circuit portion 110, a second coaxial cable 80, a first The heater energizing wire 91, the second heater energizing wire 93, the braided tube 100, and the like are included. Further, among these, the sensor body 5 includes an outer metal fitting 10, an inner metal fitting (first potential metal fitting) 30, a sensor element 60, and the like.

  In the fine particle detection system 1, the sensor body 5 is attached to a pipe attachment part EPT of an exhaust pipe EP that is made of metal and has a ground potential PVE (see FIG. 1). 2 and 3, these cables (the first coaxial cable 70, the second coaxial cable 80, the first heater energization line 91, and the second heater energization line 93) are shown so that the structure of each cable can be understood. In practice, these cables extend to the circuit unit 110 and are connected to the circuit unit 110 as shown in FIG.

  The outer metal fitting 10 of the sensor main body 5 has a cylindrical shape extending in the axial direction GH, and surrounds the inner circumference of the inner metal fitting 30 in a state of being separated from the inner metal fitting 30 and insulated. The outer metal fitting 10 is attached to the pipe attachment portion EPT of the exhaust pipe EP, which is set to the ground potential PVE, and is set to the ground potential PVE. The outer metal fitting 10 includes a mounting metal 11 and an outer cylinder 13 that is laser-welded to the mounting metal 11 on the rear end side GK.

  The mounting bracket 11 is a cylindrical member made of stainless steel. The mounting bracket 11 has a flange portion 11a that bulges outward in the radial direction and forms an outer hexagonal shape. In addition, a male screw (not shown) used for fixing the exhaust pipe EP to the pipe mounting part EPT is formed on the outer periphery of the tip part 11s on the tip side GS from the flange part 11a of the mounting bracket 11. On the other hand, a cylindrical first alumina insulating spacer 21 and a second insulating spacer 22 are held between the inner metal fitting 30 and the inner metal fitting 30 in the radial direction. Further, a cylindrical alumina sleeve 23 is disposed on the rear end side GK of the second insulating spacer 22. The rear end portion 11k of the mounting bracket 11 is crimped radially inward to press the sleeve 23 against the distal end side GS via the annular wire packing 24.

  The outer cylinder 13 is a cylindrical member made of stainless steel. A grommet 25 made of fluoro rubber is held on the radially inner side of the small-diameter portion 13a located on the rear end side GK in the outer cylinder 13. The grommet 25 is inserted with a first coaxial cable 70, a second coaxial cable 80, a first heater energizing wire 91, and a second heater energizing wire 93, which will be described later. ) To the rear end side GK. On the other hand, a distal end portion 100s of a braided tube 100, which will be described later, is disposed around the radial direction of the small-diameter portion 13a of the outer cylinder 13, and a metal ring 105, which will be described later, is further disposed around the radial direction.

  The inner metal fitting 30 has a substantially cylindrical shape extending in the axial direction GH, and is arranged on the radially inner side of the outer metal fitting 10 so as to be separated from the outer metal fitting 10 and insulated. The inner metal fitting 30 is connected to the circuit unit 110 via a first outer conductor 73 of the first coaxial cable 70 and a second outer conductor 83 of the second coaxial cable 80 described later, and has a first potential different from the ground potential PVE. PV1. The inner metal fitting 30 includes a main metal fitting 31, an inner cylinder 33, an inner cylinder connection fitting 35, an inner protector (collecting metal fitting) 37, and an outer protector 39.

  Among these, the metallic shell 31 is a cylindrical member made of stainless steel. The metal shell 31 has an annular flange portion 31a that bulges outward in the radial direction. On the other hand, a cup-shaped metal cup 41 is disposed inside the metallic shell 31 in the radial direction. A hole is formed in the bottom of the metal cup 41, and a sensor element 60 described later is inserted into the hole. Further, in the metal shell 31, a cylindrical ceramic holder 42 made of alumina and talc powder are compressed around the sensor element 60 in order from the front end GS to the rear end GK. The 1st powder filling layer 43 and the 2nd powder filling layer 44, and the cylindrical ceramic sleeve 45 which consists of alumina are arrange | positioned. The rear end portion 31k of the metal shell 31 is crimped radially inward to press the ceramic sleeve 45 against the distal end GS via an annular crimp ring 46.

The inner cylinder 33 is a cylindrical member made of stainless steel. The front end portion of the inner cylinder 33 is an annular flange portion 33 s that protrudes radially outward. The flange portion 33 s is overlapped with the flange portion 31 a of the metal shell 31, and a portion on the rear end side GK from the flange portion 33 s is laser-welded to the metal shell 31. On the other hand, on the radially inner side of the inner cylinder 40, an insulating holder 51, a first separator 52, and a second separator 53 are arranged in order from the front end side GS to the rear end side GK. Among these, the insulating holder 51 is cylindrical and made of an insulator, and is in contact with the ceramic sleeve 45 from the rear end side GK. The sensor element 60 is inserted through the insulating holder 51.
The first separator 52 is cylindrical and made of an insulator. The sensor element 60 is inserted into the first separator 52 and the tip side portion of the second potential terminal 54 is accommodated in the first separator 52. The second potential terminal 54 is in contact with the figure.

  The second separator 53 is made of an insulator and has a first insertion hole 53h1 and a second insertion hole 53h2. The first insertion hole 53h1 accommodates a rear end portion of the second potential terminal 54 and a distal end portion of a first central conductor 71 of the first coaxial cable 70 described later. The first insertion hole 53h1. Both are connected by caulking. On the other hand, in addition to the sensor element 60, the third potential terminal 55, the first heater terminal 56, and the second heater terminal 57 are accommodated in the second insertion hole 53h2 in a state of being insulated from each other. In the second insertion hole 53h2, the third potential terminal 55 contacts the third potential pad (not shown) of the sensor element 60, and the first heater terminal contacts the first heater pad (not shown) of the sensor element 60. 56 is in contact, and the second heater terminal 57 is in contact with a second heater pad (not shown) of the sensor element 60. Further, the second insertion hole 53h2 accommodates respective distal end portions of a second central conductor 81, a first heater energizing wire 91, and a second heater energizing wire 93 of a second coaxial cable 80 described later. Then, in the second insertion hole 53h2, the third potential terminal 55 and the second central conductor 81 of the second coaxial cable 80, the first heater terminal 56 and the first heater conducting wire 91, the second heater terminal 57 and the second heater. The energization wires 93 are connected by crimping.

  The inner cylinder connection fitting 35 is a stainless steel member, and is externally fitted to the inner cylinder 33 from the rear end side GK and laser-welded while surrounding the rear end portion of the second separator 53. A first coaxial cable 70, a second coaxial cable 80, a first heater energization line 91, and a second heater energization line 93 are inserted into the inner cylinder connection fitting 35. Among these, the first outer conductor 73 of the first coaxial cable 70 and the second outer conductor 83 of the second coaxial cable 80 are connected to the inner cylinder connection fitting 35 and are conductive.

  The inner protector 37 is a bottomed cylindrical stainless steel member and surrounds the distal end portion 60 s of the sensor element 60 protruding from the metal shell 31 to the distal end side GS. On the other hand, the outer protector 39 is a cylindrical member made of stainless steel, and is arranged around the inner protector 37 in the radial direction. The inner protector 37 and the outer protector 39 are externally fitted to the tip 31s of the metal shell 31 and laser welded. The outer protector 39 is formed with a plurality of gas intake ports 39h for taking the exhaust gas EG into itself, and the inner protector 37 also has a plurality of gas intakes for taking the exhaust gas EG into itself. An inlet 37h1 is formed. Furthermore, a gas discharge port 37h2 for discharging the exhaust gas EG to the outside is formed at the bottom of the inner protector 37. Note that the inner protector 37 that is set to the first potential PV1 also serves as a collection fitting for collecting floating ions CPF that have not adhered to the fine particles S.

  Next, the sensor element 60 will be described. The sensor element 60 has a plate-like shape extending in the axial direction GH, and has a ceramic base 61 in which a plurality of insulating layers made of alumina are laminated. Between the insulating layers of the ceramic base 61, a discharge electrode body 63 and an auxiliary electrode are provided. An electrode body (third potential fitting) 65 and a heater 67 are embedded and sintered together. Further, on the rear end surface of the ceramic base 61, a second potential pad connected to the discharge electrode body 63, a third potential pad connected to the auxiliary electrode body 65, a first heater pad connected to the heater 67, and a first heater pad Two heater pads are formed (not shown).

Of the discharge electrode body 63, the needle-like electrode portion 63 s that forms the tip portion protrudes from the ceramic base 61. The needle-like electrode portion 63s corresponds to the above-described “discharge electrode” having the second potential PV2, and, as will be described later, between the first potential fitting (inner fitting) 30, specifically, the inner protector 37. The ions CP to be attached to the fine particles S are generated by the air discharge generated in step (b). Therefore, in the present embodiment, the ion source is configured by the needle-like electrode portion 63 s and the inner protector 37.
On the other hand, the auxiliary electrode body 65 has a rectangular auxiliary electrode portion 65 s at the distal end side GS, and the entire auxiliary electrode body 65 is embedded in the ceramic base 61. As will be described later, the auxiliary electrode body 65 has a third potential PV3, and assists in collecting the floating ions CPF into the first potential metal fitting (inner metal fitting) 30, specifically, the collection metal fitting (inner protector) 37. This corresponds to the aforementioned “third potential metal fitting”.
The heater 67 includes a heating resistor 67 s that generates heat when energized at the front end side GS, and the entire heater 67 is embedded in the ceramic base 61.

  Next, the first coaxial cable 70 will be described. The first coaxial cable 70 extends from the outer cylinder 13 of the sensor body 5 to the circuit unit 110, and the outer side in the radial direction is surrounded by a braided tube 100 described later. A first central conductor 71 made of a copper core wire is disposed at the center of the first coaxial cable 70, and the periphery in the radial direction is covered with a first inner insulating layer 72 made of resin. Furthermore, a cylindrical first outer conductor 73 made of a braided tube knitted with a copper fine wire is disposed coaxially with the first center conductor 71 around the first inner insulating layer 72 in the radial direction. And a first outer insulating layer 74 made of resin.

The first central conductor 71 is set to the second potential PV2 by the circuit unit 110 and is electrically connected to the needle electrode part 63s of the discharge electrode body 63 that is a discharge electrode. Specifically, the distal end portion of the first central conductor 71 is caulked and connected to the second potential terminal 54 in the first insertion hole 53h1 of the second separator 53 as described above, and this second potential terminal 54 is further connected. Is in contact with a second potential pad (not shown) of the sensor element 60 connected to the discharge electrode body 63 in the first separator 52. As a result, the first central conductor 71 is electrically connected to the needle electrode portion 63 s of the discharge electrode body 63.
On the other hand, the first outer conductor 73 is set to the first potential PV1 by the circuit unit 110 and is electrically connected to the inner metal fitting 30 that is the first electric potential metal fitting. Specifically, the distal end portion of the first outer conductor 73 is connected to the inner cylinder connection fitting 35 of the inner fitting 30 as described above.

  Next, the second coaxial cable 80 will be described. The second coaxial cable 80 also extends from the outer cylinder 13 of the sensor body 5 to the circuit unit 110, and the outer side in the radial direction is surrounded by a braided tube 100 described later. A second center conductor 81 made of a copper core wire is disposed at the center of the second coaxial cable 80, and the periphery in the radial direction is covered with a second inner insulating layer 82 made of resin. Further, a cylindrical second outer conductor 83 made of a braided tube knitted with a copper fine wire is disposed coaxially with the second central conductor 81 around the second inner insulating layer 82 in the radial direction. And a second outer insulating layer 84 made of resin.

The second center conductor 81 is set to the third potential PV3 by the circuit unit 110 and is electrically connected to the auxiliary electrode body 65 which is a third potential fitting. Specifically, the distal end portion of the second central conductor 81 is caulked and connected to the third potential terminal 55 in the second insertion hole 53h2 of the second separator 53 as described above, and this third potential terminal 55 is further connected. Is in contact with a third potential pad (not shown) connected to the auxiliary electrode body 65 of the sensor element 60 in the second insertion hole 53h2. Thereby, the second center conductor 81 is electrically connected to the auxiliary electrode body 65.
On the other hand, the second outer conductor 83 is set to the first potential PV1 by the circuit unit 110 and is electrically connected to the inner metal fitting 30 that is the first potential metal fitting. Specifically, the distal end portion of the second outer conductor 83 is connected to the inner cylinder connection fitting 35 of the inner fitting 30 as described above.

  Next, the first heater conduction line 91 and the second heater conduction line 93 will be described. These first and second heater energization wires 91 and 93 are thin and single-core insulated cables, and extend from the outer cylinder 13 of the sensor body 5 to the circuit unit 110. As described above, the distal end portion of the first heater energizing wire 91 is caulked and connected to the first heater terminal 56 in the second insertion hole 53h2 of the second separator 53, and the first heater terminal 56 is further connected to the first heater terminal 56. Within the two insertion holes 53h2, the sensor element 60 is in contact with a first heater pad (not shown) connected to the heater 67. As a result, the first heater conducting wire 91 is conducted to the heater 67. Further, as described above, the tip of the second heater conducting wire 93 is caulked and connected to the second heater terminal 57 in the second insertion hole 53h2 of the second separator 53. Further, the second heater terminal 57 is Within the second insertion hole 53h2, the sensor element 60 is in contact with a second heater pad (not shown) connected to the heater 67. As a result, the second heater conducting wire 93 is conducted to the heater 67.

  Next, the braided tube 100 will be described. The braided tube 100 is a braided tube in which a stainless thin wire is knitted into a cylindrical shape, and is separate from the first coaxial cable 70, the second coaxial cable 80, the first heater conducting wire 91, and the second heater conducting wire 93. It is. The braided tube 100 extends from the outer cylinder 13 of the sensor body 5 to the circuit unit 110, and the diameters of the first coaxial cable 70, the second coaxial cable 80, the first heater conducting wire 91, and the second heater conducting wire 93. The outer side in the direction is surrounded by a gap SK.

  Since the braided tube 100 is connected to the outer metal fitting 10 attached to the exhaust pipe EP having the ground potential PVE, the braided tube 100 is set to the ground potential PVE. Specifically, the distal end portion 100 s of the braided tube 100 is disposed around the radial direction of the small diameter portion 13 a of the outer cylinder 13 in the outer metal fitting 10. On the other hand, a cylindrical metal ring 105 is disposed around the radial direction of the distal end portion 100 s of the braided tube 100. The metal ring 105 is crimped radially inward, and holds the distal end portion 100 s of the braided tube 100 between the small diameter portion 13 a of the outer cylinder 13. Thereby, the braided tube 100 is connected to the outer metal fitting 10.

Next, the electrical function and operation of the particulate detection system 1 will be described (see FIG. 5). By the circuit unit 110, the inner protector 37 of the inner metal fitting 30 is set to the first potential PV1, and the discharge electrode body 63 of the sensor element 60 is set to the second potential PV2, which is a positive potential higher than this. As a result, an air discharge (corona discharge) is generated between the inner protector 37 of the inner metal fitting (first potential metal fitting) 30 and the needle electrode portion (discharge electrode) 63s of the discharge electrode body 63, and N ³⁺ , Positive ions CP such as O ²⁺ are generated.

  On the other hand, in FIG. 5, the exhaust gas EG flowing from the left to the right in the exhaust pipe EP is taken into the outer protector 39 from the gas inlet 39h of the outer protector 39, and further through the gas inlet 37h1 of the inner protector 37. An air flow of intake gas EGI is introduced from the rear end side GK toward the front end side GS in the vicinity of the front end portion 60s of the sensor element 60, which is taken into the inner protector 37. Therefore, the generated ions CP adhere to the fine particles S in the intake gas EGI. As a result, the fine particles S become positively charged fine particles SC and flow toward the gas discharge port 37h2 together with the intake gas EGI, and are discharged to the exhaust pipe EP.

On the other hand, since the auxiliary electrode body 65 is set to the third potential PV3 by the circuit unit 110, among the generated ions CP, the floating electrode CPF that has not adhered to the fine particles S has an auxiliary electrode body (third potential metal fitting). A repulsive force is applied from the 65 auxiliary electrode portions 65 s toward the radially outer inner protector (collecting bracket) 37. Then, the floating ions CPF are attached to each part of the inner protector 37 set to the first potential PV1 to assist the collection of the floating ions CPF.
Then, the circuit unit 110 detects a signal current corresponding to the charge amount of the discharged ions CPH adhering to the charged fine particles SC discharged from the gas discharge port 37h2. Thereby, the amount (concentration) of the fine particles S contained in the exhaust gas EG can be detected.
Note that the particle detection system 1 of the present embodiment includes the heater 67 in the sensor element 60 as described above. When the heating resistor 67s of the heater 67 generates heat by energization, the tip 60s of the sensor element 60 can be heated to remove foreign matters such as water droplets and soot adhering to the tip 60s, so that the insulation of the sensor element 60 can be restored or Can be maintained.

  As described above, the particle detection system 1 includes the first coaxial cable 70 and the braided tube 100 that surrounds the radially outer side. Therefore, the first central conductor 71 that is set to the second potential PV2 and is electrically connected to the needle-like electrode portion (discharge electrode) 63s of the discharge electrode body 63 is surrounded by the first outer conductor 73 and the braided tube 100 and is shielded twice. In addition, the first outer conductor 73 which is set to the first potential PV1 and is conducted to the inner metal fitting (first electric potential metal fitting) 30 is also surrounded by the braided tube 100 and shielded.

  Furthermore, since the first coaxial cable 70 and the braided tube 100 are separate bodies, unlike the case of using a triple coaxial cable, the connection of the first central conductor 71 and the first outer conductor 73 to the sensor body 5, Connection of the braided tube 100 to the sensor body 5 can be performed independently. For this reason, the assembly of the first coaxial cable 70 and the braided tube 100 becomes easier than when a triple coaxial cable is used, and the cost can be reduced. Therefore, the particle detection system 1 can be made inexpensive.

  Further, in the present embodiment, the second coaxial cable 80 that passes through the braided tube 100 is provided. For this reason, in addition to being shielded twice by being surrounded by the second outer conductor 83 and the braided tube 100, the second central conductor 81 which is set to the third potential PV3 and is conducted to the auxiliary electrode body (third potential fitting) 65, The second outer conductor 83 which is set to the first potential PV1 and is conducted to the inner metal fitting (first electric potential metal fitting) 30 is also surrounded by the braided tube 100 and shielded.

  Furthermore, since the second coaxial cable 80 and the braided tube 100 are separate bodies, unlike the case of using a triple coaxial cable, the connection of the second center conductor 81 and the second outer conductor 83 to the sensor body 5, Connection of the braided tube 100 to the sensor body 5 can be performed independently. For this reason, the assembly | attachment of the 2nd coaxial cable 80 and the braided tube 100 becomes easier than the case where a triple coaxial cable is used, and can reduce cost. Therefore, the particle detection system 1 can be made inexpensive.

  Furthermore, in the present embodiment, the particulate detection system 1 includes first and second heater energization wires 91 and 93 that are connected to the heater 67, and the first and second heater energization wires 91 and 93 are also included in the braided tube 100. Is arranged. For this reason, the first and second heater conducting wires 91 and 93 and the first and second coaxial cables 70 and 80 can be handled together by the braided tube 100, so that the particulate detection system 1 can be easily handled.

(Deformation)
Next, a particle detection system 201 according to a modified embodiment will be described (see FIGS. 6 to 8). In the fine particle detection system 1 of the embodiment, as described above, the sensor main body 5 has the auxiliary electrode body (third potential metal fitting) 65 and the second coaxial cable 80. On the other hand, the particulate detection system 201 of this modification is different in that the sensor main body 205 does not have an auxiliary electrode body (no third potential metal fitting) and does not have a second coaxial cable.

  In the fine particle detection system 201 of this modification, the sensor main body 205 does not have an auxiliary electrode body. Specifically, the sensor element 260 of the present modification includes the discharge electrode body 63 and the heater 67 similar to those of the embodiment inside the ceramic base 261, but does not have an auxiliary electrode body. In addition, the rear surface of the ceramic base 261 has a second potential pad (not shown) connected to the discharge electrode body 63, a first heater pad and a second heater pad (not shown) connected to the heater 67. There is no third potential pad.

  In addition, since the auxiliary electrode body and the third potential pad are not present in the sensor element 260, the third potential terminal and the second coaxial cable connected to the third potential terminal are not provided. In addition, since the second coaxial cable is not provided, the shapes of the insertion holes of the inner cylinder connection fitting 235 and the grommet 225 are different from the shapes of the insertion holes of the inner cylinder connection fitting 35 and the grommet 25 of the embodiment. That is, the inner cylinder connection fitting 235 and the grommet 225 of the present modified embodiment do not have an insertion hole for inserting the second coaxial cable.

  The particulate detection system 201 of the present modification also includes the first coaxial cable 70 and a braided tube 100 that surrounds the radially outer side. For this reason, the first central conductor 71 which is set to the second potential PV2 and is conducted to the needle-like electrode portion 63s is surrounded by the first outer conductor 73 and the braided tube 100 and shielded twice, and the first potential PV1 The first outer conductor 73 that is electrically connected to the inner metal fitting 30 is also surrounded by the braided tube 100 and shielded. Furthermore, since the first coaxial cable 70 and the braided tube 100 are separate bodies, the first center conductor 71 and the first outer conductor 73 are connected to the sensor main body 205 and the braided tube 100 is connected to the sensor main body 205. Connections can be made independently. For this reason, the assembly of the first coaxial cable 70 and the braided tube 100 is facilitated, the cost can be reduced, and the particle detection system 201 can be made inexpensive. In addition, the same parts as the embodiment have the same operational effects as the embodiment. If the sensor main body 205 does not have an auxiliary electrode body as in the present modified embodiment, among the generated ions CP, the floating ions CPF that have not adhered to the fine particles S are attached to each part of the inner protector 37. In such a case, the internal structure of the inner protector 37 is appropriately improved (for example, a plurality of protrusions that protrude radially inward from the inner surface of the inner protector 37 are formed and floated). The contact chance with the ion CPF is increased), and the floating ion CPF may be easily attached to the inner protector 37.

  In the above, the present invention has been described with reference to the embodiments and modified embodiments. However, the present invention is not limited to the above-described embodiments and modified embodiments, and can be appropriately modified and applied without departing from the gist thereof. Needless to say, you can.

1,201 Particle detection system 5,205 Sensor body 10 Outer metal fitting 11 Mounting metal fitting 30 Inner metal fitting (first potential metal fitting)
37 Inside protector (collection bracket)
60,260 Sensor element 60s Tip portion 63 Discharge electrode body 63s Needle electrode portion (discharge electrode)
65 Auxiliary electrode body (third potential metal fitting)
65s Auxiliary electrode portion 67 Heater 67s Heating resistor 70 First coaxial cable 71 First central conductor 72 First inner insulating layer 73 First outer conductor 74 First outer insulating layer 80 Second coaxial cable 81 Second central conductor 82 Second Inner insulating layer 83 Second outer conductor 84 Second outer insulating layer 91 First heater conducting wire 93 Second heater conducting wire 100 Braided tube 110 Circuit part PVE Ground potential PV1 First potential PV2 Second potential PV3 Third potential EP Exhaust pipe (Vent pipe)
EG Exhaust gas (measured gas)
S Fine particle CP Ion CPF Floating ion

Claims (3)

A fine particle detection system comprising a sensor main body part that detects the amount of fine particles in a gas to be measured that is mounted on a vent pipe that is set to ground potential and circulates in the vent pipe, and a circuit part,
The sensor body is
A mounting bracket that is mounted on the vent pipe and has a ground potential;
A first potential metal fitting having a first potential different from the ground potential;
A discharge electrode that generates a second potential different from the ground potential and the first potential, and generates ions to be attached to the fine particles by air discharge generated between the first potential metal fitting and the first potential.
The particle detection system is
A first central conductor that is at the second potential and is conducted to the discharge electrode;
A first inner insulating layer covering the periphery of the first central conductor in the radial direction;
A first outer conductor that is electrically connected to the first electric potential fitting and has the first electric potential; and is arranged around the radial direction of the first inner insulating layer and coaxially with the first central conductor; and
A first outer insulating layer covering a radial circumference of the first outer conductor,
A first coaxial cable extending from the sensor body to the circuit,
Conductive to the mounting bracket to be ground potential, separate from the first coaxial cable, extends from the sensor body to the circuit portion, surrounds the radially outer side of the first coaxial cable, and is made of a fine metal wire A fine particle detection system comprising a braided tube. The particulate detection system according to claim 1,
The sensor body is
A third potential different from the ground potential, the first potential, and the second potential is used to assist in collecting the generated ions that are not attached to the fine particles into the first potential fitting. Having a third potential fitting,
The particle detection system is
A second central conductor which is set to the third potential and is conducted to the third potential fitting;
A second inner insulating layer covering the periphery of the second central conductor in the radial direction;
A second outer conductor that is electrically connected to the first potential metal fitting with the first electric potential and is arranged coaxially with the second central conductor around a radial direction of the second inner insulating layer; and
A second outer insulating layer covering the radial periphery of the second outer conductor,
A particulate detection system comprising a second coaxial cable extending from the sensor body to the circuit and passing through the braided tube. The fine particle detection system according to claim 1 or 2,
The sensor body has a heater that generates heat when energized,
The particle detection system is
A particulate detection system comprising a pair of heater energization wires that are electrically connected to the heater, extend from the sensor main body portion to the circuit portion, and pass through the braided tube.

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