JP2009109297A - Soot sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soot sensor capable of properly detecting by discharging electricity without influence of particles to contribute to conductivity other than soot even if a heating source that may burn soot is provided. <P>SOLUTION: An electrode part 322 of a center electrode 320 is opposed to the electrode part 123 of an outer electrode 120. The outer diameter of the tip part (discharge part) of the electrode part 322 is smaller than the outer diameter of a discharge part of the electrode part 123, and, further, the surface areas of the discharge parts of both electrode parts 322, 123 are in the range of 0.008-1.8 (mm<SP>2</SP>). A heater 400 is attached onto the outer peripheral surface of the tip part 630 of a cylindrical member 200. A predetermined distance in the range of 10-200 (mm) is provided between the lower edge 435 of a heat producing resistor part 431 of a heater 400 and the tip part of an electrode part 321 of the center electrode 320. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wrinkle sensor.

Conventionally, as this type of soot sensor, there is a detection unit provided in a smoke detection device disclosed in Patent Document 1 below. The smoke detection device has a rod-shaped center electrode housed in a housing through an insulator, the tip of the center electrode is exposed to the outside, and the outer electrode joined to the housing is centered through a gap. It is comprised so that it may arrange | position around the front-end | tip of an electrode. The detection unit generates a spark discharge when a high voltage is applied between the center electrode and the outer electrode with the center electrode and the outer electrode exposed in the exhaust gas.
Japanese Utility Model Publication No. 64-50355 WDE Allan, RD Freeman, GR Pucher, D. Faux and MF Bardon, `` DEVELOPMENT OF A SMOKE SENSOR FOR DIESEL ENGINES, Royal Military College of Canada, DP Gardiner, Nexum Research Corporation, p.220, Powertrain & Fluid Systems Conference, October 27-30, 2003

  By the way, in the soot sensor having the above-described configuration, by utilizing the principle that the voltage at the occurrence of spark discharge (corresponding to the discharge voltage) decreases as the amount of soot in the exhaust gas increases, The amount is detected from the discharge voltage. However, if wrinkles adhere to the insulator, the detection accuracy decreases. Therefore, it is necessary to remove the soot adhering to the insulator, but it is not sufficient to use spark discharge to remove the soot adhering to the insulator.

  On the other hand, for example, it is conceivable that the heater described in Non-Patent Document 1 is provided in the vicinity of the detection unit, and wrinkles attached to the center electrode and the outer electrode are eliminated by the heater.

  However, when the heater is provided in the vicinity of the detection unit as described above, the discharge voltage may decrease even if the center electrode and the outer electrode are exposed to exhaust gas in which almost no soot exists. In this state, the discharge voltage hardly changes even if the central electrode and the outer electrode are exposed to exhaust gas containing soot after that. For this reason, it is extremely difficult to properly detect soot based on the discharge voltage.

  When this point is examined in detail, since soot is a collection of conductive particles that are carbon particles, soot is considered to cause a decrease in discharge voltage. On the other hand, as described above, the discharge voltage is lowered even in the case of exhaust gas having almost no soot, which means that in addition to soot, the conductivity of ions and the like exhibiting substantially the same action as this soot. It is thought that there are particles that contribute.

  In view of the above, the present invention pays attention to the above, even if a heating element is provided so as to burn off the soot, by discharging without being affected by particles other than the soot that contribute to conductivity. An object of the present invention is to provide a wrinkle sensor capable of properly detecting the above.

In solving the above-mentioned problems, according to the present invention, the present invention provides a hollow electrical insulating member (200) and a front end of the electrical insulating member while being fitted in the electrical insulating member. A rod sensor comprising: a rod-like discharge electrode (320, 330, 340) having a discharge portion on the tip side, which is extended from the electrode and discharges with another member; and a heating element (430) incorporated in the electrically insulating member In
A distance of at least 10 (mm) is provided between the heating element and the tip (322, 332) of the discharge electrode, and the surface area of the discharge part is 0.008 (mm ² ) to 1.8 (mm). ² ) It is within the range.

  In such a configuration, when a high voltage is applied to the discharge electrode, the high voltage is also applied between the heating element and the discharge electrode, and discharge is also generated between the heating element and the discharge electrode. Along with this, particles that contribute to conductivity such as ions are generated.

  However, as described above, since a distance of at least 10 (mm) is provided between the heating element and the tip of the discharge electrode, the discharge part provided on the tip side of the discharge electrode is located far from the heating element. Therefore, it is difficult to reach some particles that contribute to conductivity such as ions. Therefore, particles that contribute to conductivity such as ions cannot reach the discharge part of the discharge electrode.

  Therefore, whether or not soot is present in the discharge part of the discharge electrode, the discharge voltage generated in the discharge part of the discharge electrode is not affected by the particles that contribute to the conductivity. Only drop.

Moreover, as described above, the surface area of the discharge part of the discharge electrode is within the range of 0.008 (mm ² ) to 1.8 (mm ² ). For this reason, in the vicinity of the discharge portion of the discharge electrode, the space region that occupies a high electric field strength by the discharge is narrow, and the discharge is more difficult to occur. Therefore, the discharge voltage required for discharging the discharge electrode is further increased, and the resolution in the soot sensitivity as the soot sensor is further enhanced.

As described above, a distance of at least 10 (mm) is provided between the heating element and the tip of the discharge electrode, and the surface area of the discharge part of the discharge electrode is 0.008 (mm ² ) to 1.8 (mm). Within the range of ² ). Thereby, the soot sensor can detect soot more accurately without being affected by the particles that contribute to the conductivity.

  In addition, when the discharge part of the discharge electrode is a convex surface, the surface area of the discharge part is a convex surface from a part at a distance of 0.5 (mm) in the opposite direction with respect to the top of the convex surface. Corresponds to the surface area over the top of Further, the “other member” is not particularly limited as long as it is a member that can discharge with the discharge electrode.

According to a second aspect of the present invention, there is provided a hollow electrical insulation member (200), and the electrical insulation member is fitted into the electrical insulation member via an annular gap. A soot sensor comprising a rod-like discharge electrode (360) having a discharge portion (362) extending from the tip and discharging with another member on the tip side, and a heating element (430) built in the electrically insulating member In
It has a dense sealing member (500, 600) for sealing the annular gap, and the surface area of the discharge part is within the range of 0.008 (mm ² ) to 1.8 (mm ² ). Features.

  According to this, the annular gap between the electrically insulating member and the discharge electrode is sealed with the dense sealing member. For this reason, even if particles such as ions that contribute to conductivity are generated, the particles that contribute to conductivity are encapsulated in an electrically insulating member by a dense sealing member, and are discharged into the discharge portion of the discharge electrode. I can't move.

  Therefore, whether or not soot is present in the discharge part of the discharge electrode, the discharge voltage generated in the discharge part of the discharge electrode is not affected by the particles that contribute to the conductivity. Will only drop by.

Moreover, the surface area of the discharge portion of the discharge electrodes, similarly as described claim 1, is within the range of ^{0.008 (mm 2) ~1.8 (mm} 2). For this reason, in the vicinity of the discharge part of the discharge electrode, the space region that occupies a high electric field intensity by the discharge is narrow, and the discharge is more difficult to occur. Therefore, the discharge voltage required for discharging the discharge electrode is further increased, and the resolution in the soot sensitivity as the soot sensor is further enhanced.

As described above, the annular gap between the electrically insulating member and the discharge electrode is sealed with a dense sealing member, and the surface area of the discharge portion of the discharge electrode is 0.008 (mm ² ) to It was set within the range of 1.8 (mm ² ). Thereby, the soot sensor can detect soot more accurately without being affected by the particles that contribute to the conductivity.

  In addition, when the discharge part of the discharge electrode is a convex surface, the surface area of the discharge part is from the site at a distance of 0.5 (mm) in the opposite direction with respect to the top of the convex surface. Corresponds to the surface area across the top. The “other member” is not particularly limited as long as it is a discharge electrode and a dischargeable member.

According to a third aspect of the present invention, a hollow electrical insulating member (200) is fitted into the electrical insulating member and extended from the tip of the electrical insulating member. A rod-shaped one-side discharge electrode (320, 330, 340) and one-side discharge electrode (322, 332) and the other-side discharge portion (opposite to this one-side discharge portion so as to discharge) 123) In a soot sensor comprising the other-side discharge electrode (120) having 123) and a heating element (430) incorporated in an electrically insulating member,
A distance of at least 10 (mm) is provided between the heating element and the tip of the one-side discharge electrode, and at least one of the surface areas of the one-side discharge part and the other-side discharge part is 0. It is in the range of 008 (mm ² ) to 1.8 (mm ² ).

  In such a configuration, when a high voltage is applied between the one-side discharge electrode and the other-side discharge electrode, the high voltage is also applied between the heating element and the one-side discharge electrode, A discharge is generated between the one-side discharge electrode. Along with this, particles that contribute to conductivity such as ions are generated.

  However, as described above, since a distance of at least 10 (mm) is provided between the heating element and the tip of the one-side discharge electrode, the one-side discharge portion of the one-side discharge electrode is located far from the heating element. Therefore, it is difficult to reach some particles that contribute to conductivity such as ions. Accordingly, particles that contribute to conductivity such as ions cannot reach the one-side discharge portion of the one-side discharge electrode.

  Therefore, the discharge voltage generated in the one-side discharge part of the one-side discharge electrode is affected by the particles contributing to the conductivity, whether or not soot is present in the one-side discharge part of the one-side discharge electrode. And therefore will only be reduced by wrinkles.

Moreover, as described above, at least one of the surface areas of the one-side discharge part and the other-side discharge part is within the range of 0.008 (mm ² ) to 1.8 (mm ² ). For this reason, the space region which occupies a high electric field strength by the discharge is narrow in the vicinity of at least one of the one-side discharge part and the other-side discharge part, and the discharge is further hardly generated. Accordingly, the discharge voltage required for discharging at least one of the one-side discharge electrode and the other-side discharge electrode is further increased, and the resolution in the soot sensitivity as the soot sensor is further enhanced.

As described above, a distance of at least 10 (mm) is provided between the heating element and the tip of the one-side discharge electrode, and at least one of the surface areas of the one-side discharge part and the other-side discharge part is It was set within the range of 0.008 (mm ² ) to 1.8 (mm ² ). Thereby, the soot sensor can detect soot more accurately without being affected by the particles that contribute to the conductivity.

  In addition, when the one side discharge part of the one side discharge electrode is a convex surface, the surface area of the one side discharge part is a distance of 0.5 (mm) in the opposite direction with respect to the top part of the convex surface. It corresponds to the surface area from the part to the top of the convex surface. On the other hand, when the other discharge part of the other discharge electrode has a convex surface, the surface area of the other discharge part is 0.5 (in the opposite direction with respect to the top of the convex surface of the other discharge part). mm), which corresponds to the surface area from the site at a distance of (mm) to the top of the convex surface.

According to the present invention, in the description of claim 4, a hollow electrical insulating member (200) is fitted into the electrical insulating member via an annular gap, and the electrical insulating member A rod-like one-side discharge electrode (360) extending from the tip, and one-side discharge part (362) of the one-side discharge electrode and the other-side discharge part (123) facing this one-side discharge part so as to discharge. In the soot sensor, comprising: the other-side discharge electrode (120) having a) and a heating element (430) incorporated in the electrically insulating member,
It has a dense sealing member (500, 600) for sealing the annular gap, and at least one of the surface areas of the one-side discharge part and the other-side discharge part is 0.008 (mm ² ) to It is characterized by being in the range of 1.8 (mm ² ).

  According to this, the annular gap between the electrically insulating member and the one-side discharge electrode is sealed with the dense sealing member. For this reason, even if particles such as ions that contribute to conductivity are generated, the particles that contribute to conductivity are encapsulated in an electrically insulating member by a dense sealing member, and one side of the one-side discharge electrode It cannot move to the discharge part.

  Therefore, whether or not soot is present in the one-side discharge part of the one-side discharge electrode, the discharge voltage generated in the one-side discharge part of the one-side discharge electrode is affected by particles that contribute to conductivity. So it is only reduced by wrinkles.

Moreover, at least one of the surface areas of the one-side discharge part and the other-side discharge part is within a range of 0.008 (mm ² ) to 1.8 (mm ² ). For this reason, the discharge voltage required for discharging at least one of the one-side discharge electrode and the other-side discharge electrode is further increased, and the resolution of the soot sensitivity as the soot sensor is further enhanced.

As described above, the annular gap between the electrically insulating member and the one-side discharge electrode is sealed with a dense sealing member, and at least one of the surface areas of the one-side discharge part and the other-side discharge part. One surface area was set within the range of 0.008 (mm ² ) to 1.8 (mm ² ). Thereby, the soot sensor can detect soot more accurately without being affected by the particles that contribute to the conductivity.

  In addition, when the one side discharge part of the one side discharge electrode is a convex surface, the surface area of the one side discharge part is a distance of 0.5 (mm) in the opposite direction with respect to the top part of the convex surface. It corresponds to the surface area from the part to the top of the convex surface. On the other hand, when the other discharge part of the other discharge electrode has a convex surface, the surface area of the other discharge part is 0.5 (in the opposite direction with respect to the top of the convex surface of the other discharge part). mm), which corresponds to the surface area from the site at a distance of (mm) to the top of the convex surface.

According to the fifth aspect of the present invention, in the soot sensor according to the third or fourth aspect, one of the one-side discharge electrode and the other-side discharge electrode is an anode and the other is a cathode. The surface area of the discharge part is within the range of 0.008 (mm ² ) to 1.8 (mm ² ), and the surface area of the discharge part of the cathode is 0.07 (mm ² ) or more. .

According to this, even when one of the one-side discharge electrode and the other-side discharge electrode is used as an anode and the other discharge electrode is used as a cathode, the surface area of the cathode is 0.07 (mm ² ) or more as described above. Thus, the cathode is not easily damaged by discharge as compared with the anode, and the effect of the invention according to claim 3 or 4 is maintained while maintaining good durability like the anode. Can be achieved. More preferably, the surface area of the anode is 0.12 (mm ² ) or more.

According to a sixth aspect of the present invention, in the scissor sensor according to any one of the third to fifth aspects, the hollow metal fitting (110) formed by fitting an electrically insulating member is provided. prepare for,
The one-side discharge electrode is a center electrode (320, 330, 360) fitted to the electrically insulating member so as to extend from the tip portion, and the other-side discharge electrode is an outer electrode extending from the tip of the metal fitting. (120).

  Even with such a configuration, it is possible to achieve the same effect as that of the invention described in any one of claims 3 to 5.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

Hereinafter, each embodiment of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 shows a first embodiment of a wrinkle sensor according to the present invention. This wrinkle sensor mainly includes a metal shell 110, an outer electrode 120, a cylindrical member 200, and a center electrode 320.

  The metal shell 110 is formed in a cylindrical shape from a mild steel material. The metal shell 110 includes a base end side metal part 111 and a front end side metal part 112 having an inner diameter smaller than that of the base end side metal part 111. Prepare. Further, a flange 113 is formed between the proximal end metal fitting 111 and the distal metal fitting 112, and the inner peripheral surface of the proximal metal fitting 111 is formed on the inner peripheral surface of the flange 113. An inclined portion 114 that extends toward the surface is provided.

  The proximal end portion 121 of the outer electrode 120 is welded to the distal end 115 of the distal end side metal part 112 and extends parallel to the axis of the front end side metal part 112. The distal end portion 122 of the outer electrode 120 extends from the proximal end portion 121 to the axial center side of the metallic shell 110 and faces the distal end 115 of the distal end side metal portion 112. Further, the electrode portion 123 of the outer electrode 120 is welded onto the surface of the distal end portion 122 facing the distal end 115 of the distal end side metal fitting portion 112 so as to be coaxially opposed to the center electrode 320 (described later). As the material of the outer electrode 120, stainless steel, pure nickel, nickel alloy, pure copper or copper alloy, or a noble metal such as iridium or platinum is adopted.

  Here, the discharge part facing the center electrode 320 of the electrode part 123 is a plane (hereinafter also referred to as a discharge surface) orthogonal to the axis of the center electrode 320. Moreover, the outer diameter and axial length of this electrode part 123 are 2.0 (mm) and 1.5 (mm), respectively, for example. The axial length may be 0.5 (mm), but is preferably 1.5 (mm) or more together with the axial length of the electrode portion 321 (described later) of the center electrode 320. As a result, the discharge voltage can be further increased and the soot sensitivity can be further increased. Note that platinum or nickel is used as the material of the discharge part 123. The outer electrode 120 is used as a negative electrode.

  The tubular member 200 is formed of an electrically insulating material such as ceramic, and the tubular member 200 includes a proximal end portion 210, an intermediate portion 220, and a distal end portion 230. The intermediate part 220 is formed between the proximal part 210 and the distal part 230 so as to have a larger outer diameter than the proximal part 210 and the distal part 230. For this reason, the outer peripheral surface of the intermediate portion 220 is inclined at both axial ends toward the outer peripheral surface of the proximal portion 210 and the large-diameter portion 231 (described later) of the distal portion 230, respectively. The inclined portions 221 and 222 are configured.

  As shown in FIG. 1, the distal end portion 230 is configured with a large diameter portion 231 and a small diameter portion 232 that are coaxially and integrally formed with each other. The large diameter portion 231 extends from the intermediate portion 220, while the small diameter portion 232 extends from the large diameter portion 231. In the first embodiment, the small diameter portion 232 is formed so as to be inclined from the end portion on the large diameter portion 231 side to the tip end portion.

  Of the cylindrical member 200 configured as described above, the distal end portion 230 is inserted through the distal end fitting portion 112 of the metal shell 110. Further, the intermediate side portion 220 is fitted into the base end side metal fitting portion 111 of the metal shell 110, and the inclined surface portion 222 of the intermediate side portion 220 is made of metal on the inclined portion 114 of the distal end side metal fitting portion 112. It is seated via the packing 116. Thereby, the cylindrical member 200 is coaxially supported in the metal fitting member 100. Further, the large-diameter portion 231 of the cylindrical member 200 is fitted to the distal end side metal fitting portion 112 of the metal fitting member 100. Note that the opening 117 of the proximal end metal part 111 is fastened to the inclined surface part 221 of the intermediate part 220 of the cylindrical member 200 by caulking.

  The terminal member 310 is coaxially connected to a center electrode 320 (described later), and this terminal member 310 has an electric terminal that connects the center electrode 320 to a high-voltage circuit (not shown) at a base end portion 311 thereof. The connecting end is configured.

  As shown in FIG. 1, the center electrode 320 includes an electrode base 321 and a linear electrode portion 322. The electrode base 321 extends from the distal end side portion 230 of the cylindrical member 200 toward the electrode portion 123 of the outer electrode 120. The electrode base 321 is formed with a notch 323 in which the tip of the electrode base 321 is cut out in a semi-cylindrical shape in order to facilitate welding of the electrode part 322 to the electrode base 321. The electrode base 321 is made of stainless steel, for example, so as to have an outer diameter of 2.5 (mm).

  The electrode part 322 is attached by welding or the like along the axial end surface 324 of the notch part 323 of the electrode base body 321, with a predetermined discharge gap (for example, 0.5 (mm)), and the electrode part of the outer electrode 120. It faces the part 123. Thereby, both electrode parts 322 and 123 generate | occur | produce a discharge in the said soot sensor via the said discharge gap.

  Here, the electrode part 322 is formed of a columnar wire such as nickel (Ni) or platinum (Pt), and the discharge part formed on the tip side of the electrode part 322 is orthogonal to the axis of the electrode part 322. It is a flat surface (hereinafter also referred to as a discharge surface). Moreover, the outer diameter of this electrode part 322 is 0.5 (mm), for example. Moreover, the extension length from the notch part 323 is 1.5 (mm) among the axial lengths of this electrode part 322, for example. The center electrode 320 is used as a positive electrode.

  Thus, in the soot sensor, when a high voltage is applied between the center electrode 320 and the outer electrode 120 from the high voltage circuit, the discharge is caused by the electrode portion 322 of the center electrode 320 and the electrode portion 123 of the outer electrode 120. Occurs between.

  In the first embodiment, the high voltage is a voltage that causes dielectric breakdown of the air between the electrode parts 123 and 322 and generates a discharge between the electrode parts 123 and 322, assuming the above-described discharge gap, for example, 10 (kV) is set. Thereby, the voltage applied between the electrode portions 322 and 123 is detected as a voltage during discharge (hereinafter also referred to as a discharge voltage). Note that the discharge voltage decreases when there is a flaw between the electrode portions 322 and 123.

  As shown in FIG. 1, the wrinkle sensor includes a heater 400, and the heater 400 is attached to the entire circumference of the small diameter portion 232 of the distal end portion 230 of the cylindrical member 200. Thereby, the heater 400 plays the role which prevents the short circuit by the wrinkles of both the electrode parts 123 and 322 by performing the heat cleaning of both the electrode parts 123 and 322.

  The heater 400 includes two alumina sheets 410 and 420 and a heating element 430 as shown in FIG. The heating element 430 includes a strip-shaped outer heating resistor portion 431, a strip-shaped inner heating resistor portion 432, and positive and negative electrode pads 433 and 434. The heating resistor portions 431 and 432 together with the electrode pads 433 and 434, respectively. The platinum paste is formed on the inner surface of the alumina sheet 410 by printing and baking with each predetermined pattern as shown in FIG.

  Here, the positive electrode pad 433 is connected to one end of each of the heat generating resistor portions 431 and 432 and serves as a positive connection terminal of the heater 400. On the other hand, the negative electrode pad 434 is connected to the other end of each of the heat generating resistor parts 431 and 432 and serves as a negative connection terminal of the heater 400.

  In the heater 400 configured as described above, when the soot is deposited on the cylindrical member 200 to such an extent that proper discharge between the electrode parts 123 and 322 is prevented, the heating element 430 is removed from the heater drive circuit (not shown). The heater voltage (for example, 15 (V)) is applied to generate heat and perform the heat cleaning. This heat cleaning is performed in a state where the application of high voltage from the high voltage circuit to both electrode portions 123 and 322 is stopped.

  In the first embodiment, a length of 3 (mm) is provided between the lower edge portion 435 of the heating resistor portion 431 and the distal end of the distal end portion 230 of the cylindrical member 200.

  The reason why the length of 3 (mm) is provided in this way is to prevent a phenomenon in which the heater 400 is short-circuited with the vicinity of the distal end portion of the cylindrical member 200 in the center electrode 320 or discharge occurs. is there. Moreover, in order to prevent the phenomenon that improper accumulation of soot occurs on the distal end side of the cylindrical member 200, it is desirable that it is 12 (mm) or less.

  Further, as shown in FIG. 1, the wrinkle sensor has positive and negative side leads 440 and 450 for the heater 400 and a glass film 460. The positive lead 440 has an axial lead portion 441 and a circumferential lead portion 442, and the axial lead portion 441 is provided along a predetermined axial portion (see FIG. 1) of the outer peripheral surface of the cylindrical member 200. It has been.

  The axial lead portion 441 extends along the cylindrical member 200 and extends to the outside of the metal shell 110. Note that the tip end portion 443 of the axial lead portion 441 is electrically connected to the electrode pad 423 via a through-hole portion 421 (see FIG. 2) formed in the alumina sheet 420 of the heater 400.

  Further, the circumferential lead portion 442 is provided on the outer peripheral surface of the proximal end portion 210 of the tubular member 200 over the entire circumference outside the metal shell 110, and the circumferential lead portion 442 is formed of the glass film 460. Is electrically connected to the axial lead portion 441.

  The negative lead 450 is provided on the outer peripheral surface of the cylindrical member 200 via the glass film 460, and the negative lead 450 includes an axial lead portion 451 and a circumferential lead portion 452. The axial lead portion 451 extends along the cylindrical member 200. Note that the tip end portion 453 of the axial lead portion 451 is electrically connected to the electrode pad 424 via a through-hole portion 422 (see FIG. 2) formed in the alumina sheet 420 of the heater 400.

  The circumferential lead portion 452 is provided along the circumferential direction of the inclined portion 222 of the cylindrical member 200 and separated from the axial lead portion 441 via the glass film 460. The circumferential lead portion 452 is electrically connected to the axial lead portion 451.

  The glass film 460 passes through the back surface side of the negative lead 450 and covers the axial lead portion 441 (excluding the front end portion 443), so that the heater 400 of the front end portion 230 of the outer peripheral surface of the cylindrical member 200 is covered. It is provided on the entire circumference from the upper edge to the base end side portion 210 through the intermediate side portion 220. Thereby, the glass film 460 plays a role of electrically insulating the cylindrical member 200 and the axial lead portion 441 from the metal shell 110.

Next, in the first embodiment, a configuration adopted to discharge the wrinkle sensor without being affected by particles contributing to conductivity other than wrinkles and to further increase wrinkle sensitivity will be described.
1. First, in this configuration, the distance between the lower edge portion 435 of the heat generating resistor portion 431 of the heater 400 and the tip portion (the tip surface) of the linear electrode portion 322 of the center electrode 320 is at least 10 (mm). ) Or more and 200 (mm) or less (25 (mm) in this embodiment).

  When the distance is less than 10 (mm), when a high voltage is applied between the outer electrode 120 and the central electrode 320, the cylindrical member 200 and the space between the cylindrical member 200 and the central electrode 320 are removed. Also, it is applied between the heater 400 and the center electrode 320. Along with this, a discharge is also generated between the distal end portion 230 of the cylindrical member 200 and the center electrode 320.

  When this discharge becomes corona discharge, it is presumed that the gas existing between the tip portion 230 of the cylindrical member 200 and the center electrode 320 is ionized to generate ions. The ions generated in this manner move from the inside of the distal end side portion 230 of the cylindrical member 200 toward the electrode portion 322 side of the center electrode 320, and in the same manner as the heel, both the electrode portions 322 are electrically connected. , 123 are presumed to act as particles that contribute to conductivity.

  This induces a discharge phenomenon similar to that in which the atmosphere contains soot even if the atmosphere between the electrode portions 322 and 123 contains not the soot but the soot and causes a decrease in the discharge voltage. Means that. In other words, even if no soot is present, the presence of ions causes the same drop in discharge voltage as when soot is present, so it is difficult to correctly detect the presence of soot and the amount of soot from the discharge voltage. It is.

  On the other hand, if the tip of the electrode part 322 is outside the movable range of the ions, it is presumed that the atmosphere does not contain the ions and that the detection accuracy of soot can be ensured appropriately. The

  Considering the above, when the relationship between the heel sensitivity of the heel sensor of the first embodiment and the distance is examined by changing this distance to various values, it is at least 10 mm or more. Then, it was found that the above-described ions are in a range where they cannot move to the tip of the electrode part 322. And if it was in this range, it turned out that a wrinkle sensor can exhibit a substantially appropriate wrinkle sensitivity.

Moreover, it is desirable that the distance is 200 (mm) or less. This is because if the length is longer than 200 mm, it is difficult to install the soot sensor on the exhaust pipe of the automobile engine.
2. Second, the surface area of the discharge part (discharge surface) of the electrode part 322 is smaller than the surface area of the discharge part (discharge surface) of the electrode part 123, and the surface area of the discharge part (discharge surface) of the electrode part 322 and the electrode The surface areas of the discharge part (discharge surface) of the part 123 are both within the range of 0.008 (mm ² ) to 1.8 (mm ² ). Hereinafter, the reason for this will be described.
(1) First, the outer diameter of the electrode part 123 of the outer electrode 120 was made constant, and the wrinkle sensitivity when the outer diameter of the electrode part 322 of the center electrode 320 was changed was measured. Prior to this measurement, Examples 1 to 5 were prepared as samples as shown in Table 1 below, and Comparative Examples 1 and 2 were prepared for comparison with these Examples.

ここで、各実施例１〜５並びに各比較例１及び２の構成は、中心電極及び外側電極の各電極部を除き、本第１実施形態における煤センサの構成（図１参照）と同様である。

Here, the configurations of Examples 1 to 5 and Comparative Examples 1 and 2 are the same as the configuration of the wrinkle sensor in the first embodiment (see FIG. 1) except for the electrode portions of the center electrode and the outer electrode. is there.

  Moreover, the outer diameter of the electrode part of the center electrode of each Example 1-5 is changed as shown in Table 1 within the range of 0.1 (mm)-1.5 (mm), respectively. On the other hand, the outer diameters of Comparative Examples 1 and 2 are 2.0 (mm) and 2.5 (mm), respectively, as shown in Table 1.

  However, in each Example 1-5, the axial length (extension length from the front-end | tip part of an electrode base | substrate) of the electrode part of a center electrode is 1.5 (mm). Moreover, the distance between the lower edge part of the heating resistor of the heater and the tip part (tip face) of the linear electrode part of the center electrode is 25 (mm). This distance is 5 (mm) in each of Comparative Examples 1 and 2. In each of Examples 1 to 5, the material for forming the electrode portion of the center electrode is pure nickel (pure Ni).

  Moreover, in each Example 1-5, the outer diameter and axial length of the electrode part of an outer side electrode are 1.6 (mm) and 0.5 (mm), respectively. Note that the material for forming the electrode portion of each outer electrode is an alloy of platinum and nickel (Pt—Ni), for example, an alloy made of 90Pt-10Ni. In each of Examples 1 to 5 and Comparative Examples 1 and 2, the discharge gap is 0.5 (mm).

Under such a premise, the wrinkle sensitivity of each of Examples 1 to 5 and Comparative Examples 1 and 2 was measured under the following wrinkle sensitivity measurement conditions and wrinkle sensitivity measurement method.
煤 Sensitivity measurement conditions:
The temperature of the gas to which each of Examples 1 to 5 and Comparative Examples 1 and 2 is exposed is 100 (° C.). The composition of the gas was 37.5% argon (Ar), 10% oxygen (O ₂ ), 5% carbon dioxide (CO ₂ ), 5% water (H ₂ O). ) And nitrogen (N ₂ ).
煤 Sensitivity measurement method:
This soot sensitivity measuring method was carried out with each of Examples 1 to 5 and Comparative Examples 1 and 2 being exposed to the gas having the above composition, with the center electrode serving as an anode or a negative electrode, and a soot concentration of 0 (mg / m ³ ) and The wrinkle sensitivity was measured by changing to 2 (mg / m ³ ).

However, the soot sensitivity is expressed by a value obtained by subtracting the discharge voltage at the soot concentration of 2 (mg / m ³ ) from the discharge voltage at the soot concentration of 0 (mg / m ³ ).

  Thus, when the wrinkle sensitivity of each of Examples 1 to 5 and Comparative Examples 1 and 2 was measured by the wrinkle sensitivity measurement method under the wrinkle sensitivity measurement conditions, the results shown in Table 1 were obtained. It was.

  According to Table 1, when the center electrode is either an anode or a negative electrode, the wrinkle sensitivities of Comparative Examples 1 and 2 are 0.253 (kV), 0.726 (kV), and 2 (kV). It can be seen that the wrinkle sensitivity of Examples 1 to 5 is in the range of 3.060 (kV) to 5.189 (kV) and is considerably higher than 2 (kV). . Note that 2 (kV) described above is a lower limit value required as appropriate wrinkle sensitivity as a wrinkle sensor.

  In other words, in each of Examples 1 to 5, the outer diameter of the electrode portion of the outer electrode is 1.6 (mm), and the outer diameter of the electrode portion of the center electrode is 0.1 (mm) to 1.5 ( mm), it can be seen that the wrinkle sensitivity of each of Examples 1 to 5 is obtained as a value considerably higher than 2 (kV).

Then, the outer diameter range 0.1 (mm) to 1.5 (mm) of the electrode part of the center electrode in each of Examples 1 to 5 is converted into the surface area of the discharge part (discharge surface) of the electrode part of the center electrode. For example, this surface area is within the range of 0.008 (mm ² ) to 1.8 (mm ² ). On the other hand, if the outer diameter range 2 (mm) to 2.5 (mm) of the electrode part of the center electrode in each of Comparative Examples 1 and 2 is converted into the surface area of the discharge part (discharge surface) of the electrode part of the center electrode, This surface area is within the range of 3.1 (mm ² ) to 4.9 (mm ² ).

Here, the lower limit value of the surface area of the discharge part (discharge surface) in the electrode part of the center electrode is set to 0.008 (mm ² ), if it is smaller than 0.008 (mm ² ), the electrode part of the center electrode This is because there is a risk of melting.

According to the above, the surface area within the range of 0.008 (mm ² ) to 1.8 (mm ² ) is the tip (tip surface) of each electrode portion of the center electrode and the outer electrode of each of Examples 1 to 5. If it exists, it turns out that the favorable value of 2 (kV) or more is obtained as wrinkle sensitivity of a wrinkle sensor.
(2) Next, the wrinkle sensitivity when the outer diameter of the electrode portion of the outer electrode is changed while the outer diameter of the electrode portion of the center electrode is made constant based on the wrinkle sensitivity measurement condition. And the wear amount of the electrode part of the outer electrode as the cathode was measured by the following durability test method.
Endurance test conditions:
This durability test condition is a cathode wear test in which the outer electrode is used as a cathode, and discharge is performed in the atmosphere for a predetermined continuous discharge time (5 hours), and the wear amount of the electrode portion of the outer electrode before and after this discharge is measured with a magnifying glass. Is the condition.

  Prior to this measurement, Examples 6 to 14 were prepared as samples as shown in Table 2 below.

ここで、各実施例６〜１４の構成は、上述の各実施例１〜５と同様に、中心電極及び外側電極の各電極部を除き、本第１実施形態における煤センサの構成（図１参照）と同様である。

Here, the configurations of Examples 6 to 14 are the same as those of Examples 1 to 5 described above, except for the electrode portions of the center electrode and the outer electrode, and the configuration of the wrinkle sensor in the first embodiment (FIG. 1). See).

  In each of Examples 6 to 14, the outer diameter of the electrode portion of the center electrode is constant at 0.4 (mm) as shown in Table 2. The material for forming the electrode portion of each center electrode is pure nickel (pure Ni). Moreover, the distance between the lower edge part of the heating resistor of the heater and the tip part (tip face) of the electrode part of the center electrode is 25 (mm).

  Moreover, in each Example 6-14, as shown in Table 2, the outer diameter of the electrode part of an outer side electrode was changed within the range of 0.1 (mm)-2.0 (mm). Moreover, the axial length of the electrode part of each outer electrode is 1.5 (mm). The material for forming the electrode portion of the outer electrode is pure platinum. In each of Examples 6 to 14, the discharge gap is 0.5 (mm).

  Under such a premise, when the wrinkle sensitivity of each of Examples 6 to 14 was measured by the above wrinkle sensitivity measurement method under the above wrinkle sensitivity measurement conditions, the results shown in Table 2 were obtained. It was. According to this, it can be seen that the wrinkle sensitivity of each of Examples 6 to 14 is in the range of 2.882 (kV) to 5.522 (kV), and both are 2 (kV) or more.

  In other words, in each of Examples 6 to 14, the outer diameter of the electrode portion of the center electrode is 0.4 (mm), and the outer diameter of the electrode portion of the outer electrode is 0.1 (mm) to 2.0 ( mm), it can be seen that a good wrinkle sensitivity of 2 (kV) or more can be obtained.

  Moreover, when the durability test by the said durability test conditions was given about each Examples 6-14 and the abrasion loss of the electrode part of the outer side electrode in each Examples 6-14 was measured, the result shown in Table 2 was obtained. According to this, in Example 6, the wear amount of the electrode part of the outer electrode is large as 354 (μm), whereas in each of Examples 7 to 14, the wear amount of the electrode part of the outer electrode is 10 (μm). It was found to be within the range of ˜32 (μm) and greatly reduced as compared with Example 6. Therefore, in Example 6, it can be said that the electrode part of the outer electrode lacks durability.

According to the above, the surface area of the discharge part (discharge surface) of the electrode part 322 of the center electrode 320 is smaller than the surface area of the discharge part (discharge surface) of the electrode part 123 of the outer electrode 120, and each electrode part 322, If the surface areas of the 123 discharge parts (discharge surfaces) are both within the range of 0.008 (mm ² ) to 1.8 (mm ² ), the soot sensitivity as a soot sensor can be obtained satisfactorily.

According to the first embodiment configured as described above, even if the soot sensor generates ions in the distal end portion 230 of the cylindrical member 200 due to the discharge based on the application of a high voltage, the heating resistance of the heater 400 Since there is a distance of 25 (mm) between the lower edge portion 435 of the portion 431 and the tip of the electrode portion 321 of the center electrode 320, the discharge voltage is not affected by the ions, and therefore is Only drop. Furthermore, the surface area of the discharge portion of the electrode sections 322,123 is due to within the range of ^{0.008 (mm 2) ~1.8 (mm} 2), resolution in the soot sensitivity of the soot sensor further enhanced . As a result, even if the soot sensor is exposed to the exhaust gas of the engine of a diesel internal combustion engine, soot in the exhaust gas can be detected with higher accuracy without being affected by ions.
(Second Embodiment)
FIG. 3 shows a main part of the second embodiment of the present invention. In the second embodiment, the center electrode 330 is employed in place of the center electrode 320 described in the first embodiment. The center electrode 330 includes an electrode base 331 and an electrode portion 332, and the electrode base 331 is coaxially connected to the terminal member 310, so that the electrode portion of the outer electrode 120 extends from the distal end portion 230 of the cylindrical member 200. It extends toward 123. Here, the tip surface of the electrode base 331 is a plane orthogonal to the axis of the electrode portion 123.

  The electrode portion 332 is welded to the electrode base 331, and this electrode portion 332 faces the electrode portion 123 of the outer electrode 120 with a discharge gap. Here, the axial length of the electrode part 322 is 1.5 (mm), for example. Other configurations are the same as those in the first embodiment.

According to the second embodiment configured as described above, in the electrode base 331, the electrode section 332 is extended from the distal end surface of the electrode base 331, thereby achieving the same effect as the first embodiment. Can do.
(Third embodiment)
FIG. 4 shows a main part of the third embodiment of the present invention. In the third embodiment, the center electrode 340 is employed instead of the center electrode 320 described in the first embodiment.

  As shown in FIG. 4, the center electrode 340 is connected to the terminal member 310 in the distal end portion 230 of the cylindrical member 200, and the central electrode 340 is connected to the outer electrode from the distal end portion 230 of the cylindrical member 200. It extends toward 120 electrode parts 123.

  Here, as shown in FIG. 4, the center electrode 340 is formed with the same linear material as the electrode portion 322 of the center electrode 320 so as to be tapered gradually from the distal end side portion 230 side to the electrode portion 123 side. Has been. In the third embodiment, the discharge part of the center electrode 340 is configured with a plane (discharge surface) orthogonal to the axis of the electrode part 123, similarly to the discharge part of the electrode part 322. Further, the outer diameter of the discharge part of the center electrode 340 is the same as the outer diameter of the discharge part of the electrode part 322. Other configurations are the same as those in the first embodiment.

According to the third embodiment configured as described above, the center electrode 340 plays the same role as the electrode portion 322. As a result, the same effect as the first embodiment can be achieved.
(Fourth embodiment)
FIG. 5 shows a fourth embodiment of the present invention. In the fourth embodiment, the center electrode 360 is employed instead of the center electrode 330 described in the second embodiment, and the sealing member 500 is additionally employed. In the fourth embodiment, in order to clearly show the cross-sectional shape of the distal end side portion 230 of the cylindrical member 200, the shape as the heel sensor is enlarged and drawn in a direction perpendicular to the axis of the heel sensor. It is.

  The center electrode 360 includes an electrode base 361 and an electrode part 362, and the electrode base 361 is connected to the terminal member 310 and extends from the distal end portion 230 of the cylindrical member 200 toward the electrode part 123 of the outer electrode 120. Has been issued. Here, the tip surface of the electrode base 361 is a plane orthogonal to the axis of the electrode portion 123. Further, the electrode base 361 is considerably shorter than the electrode base 331 and extends from the distal end portion of the distal end portion 230 of the cylindrical member 200 to such an extent that the sealing member 500 can be attached. The electrode part 362 extends from the electrode base 361 and faces the electrode part 123 of the outer electrode 120 with a discharge gap.

  The sealing member 500 is formed in a hollow truncated cone shape in cross section, and is mounted so as to close the distal end opening surface 234 of the distal end side portion 230 of the cylindrical member 200. Here, the sealing member 500 is hermetically adhered to the outer peripheral surface of the electrode base 361 and the front end opening surface 234 of the front end side portion 230 of the cylindrical member 200 at the bottom surface 501 and the hollow portion inner peripheral surface 502.

  The sealing member 500 configured as described above is formed as follows. First, glass powder (made mainly of SiO2, B2O3 and ZnO) manufactured by Asahi Glass Co., Ltd. is prepared, and this powder is made into a paste to produce a glass powder paste. This glass manufactured by Asahi Glass Co., Ltd. is characterized by high density and high heat resistance. Here, the high density means a density sufficient to prevent the ions from passing through the forming material of the sealing member 500. Further, the high heat resistance refers to heat resistance that the forming material of the sealing member 500 can withstand the heating temperature of the heater 400 (for example, 500 (° C.) to 700 (° C.)).

  The glass powder paste produced as described above is applied in a truncated cone shape across the outer peripheral surface of the electrode base 361 and the distal end opening surface 234 of the distal end side portion 230 of the cylindrical member 200, and is fired under predetermined firing conditions. Thus, the sealing member 500 is formed. Other configurations are the same as those of the third embodiment.

  According to the fourth embodiment configured as described above, the sealing member 500 seals the opening of the distal end opening surface 234 of the cylindrical member 200 based on the denseness thereof, thereby allowing the ions to flow into the cylindrical member. It is contained in the interior of 200, and the movement of the ions to the tip of the central electrode 360 is prohibited. Moreover, the electrode part 362 plays the same role as the electrode part 332, so that the resolution in the eyelid sensitivity as the eyelid sensor is further increased.

Thereby, even if the soot sensor is installed in the exhaust pipe of the engine, soot in the exhaust gas can be detected with higher accuracy without being affected by particles contributing to conductivity.
(Fifth embodiment)
FIG. 6 shows a fifth embodiment of the present invention. In the fifth embodiment, a cylindrical sealing member 600 is employed instead of the sealing member 500 described in the fourth embodiment.

  The sealing member 600 is coaxially fitted in an annular gap formed between the electrode base 361 of the center electrode 360 and the cylindrical member 200. The sealing member 600 formed in this way is filled with a glass powder paste between the electrode base 361 and the cylindrical member 200 and fired. Thereby, the cylindrical sealing member 600 is formed. Therefore, the sealing member 600 is hermetically adhered to the outer peripheral surface of the electrode base 361 and the inner peripheral surface of the cylindrical member 200 at the inner peripheral surface 601 and the outer peripheral surface 602. Other configurations are the same as those in the fourth embodiment.

  According to the fifth embodiment configured as described above, the sealing member 600 is fitted so as to tightly adhere to the outer peripheral surface of the electrode base 361 and the inner peripheral surface of the cylindrical member 200. The sealing member 600 extends from the distal end opening surface 234 of the cylindrical member 200 toward the proximal end of the distal end side portion 230 through the inner peripheral side of the heater 400.

  For this reason, even if discharge is generated between the heater 400 and the electrode base 361 of the center electrode 360 and ions are generated in the distal end portion 230 of the cylindrical member 200, the ions are generated by the sealing member 600. Due to the high density, the tube member 200 is well contained in the distal end portion 230. Therefore, the ions are prohibited from moving to the tip of the center electrode 360.

  Moreover, the electrode part 362 plays the same role as the electrode part 332, so that the resolution in the eyelid sensitivity as the eyelid sensor is further increased. Thereby, even if the soot sensor is installed in the exhaust pipe of the engine, soot in the exhaust gas can be detected with higher accuracy without being affected by the particles that contribute to the conductivity.

In carrying out the present invention, the following various modifications are possible without being limited to the above embodiments.
(1) The forming material of the electrode part 322 of the center electrode 320 and the electrode part 123 of the outer electrode 120 is not limited to those described in the above embodiments, and various materials used for the spark plug, for example, Pt, It may be a noble metal such as Ir or Rh, Ni or W.
(2) In carrying out the present invention, unlike each embodiment, the surface area of at least one of the discharge portions of both the electrode portions of the center electrode and the outer electrode is 0.008 (mm ² ). It should just be in the range of -1.8 (mm < ² >).
(3) In carrying out the present invention, contrary to each embodiment, the surface area of the discharge part of the electrode part of the center electrode may be larger than the surface area of the discharge part of the electrode part of the outer electrode.
(4) In carrying out the present invention, in the center electrode or the outer electrode as the cathode, the surface area of the discharge part of the electrode part may be 0.07 (mm ² ) or more. This prevents the electrode part of the center electrode or the outer electrode as a cathode from melting faster than the electrode part of the center electrode or the outer electrode as an anode, and maintains the durability of the cathode as long as the anode. be able to.
(5) The outer shape of each electrode portion of the center electrode and the outer electrode described in each of the above embodiments may be, for example, a columnar shape, a quadrangular prism shape, a triangular prism shape, or a column shape having a trapezoidal section, The discharge part of each electrode part of a center electrode and an outer electrode is not restricted to a plane, A cone shape, a triangular pyramid shape, a quadrangular pyramid shape, a hemispherical shape, etc. may be sufficient.
(6) In carrying out the present invention, the heater 400 may be eliminated by incorporating the heating element 430 in the cylindrical member 200.

It is a partial section side view showing a 1st embodiment of a spark plug type bag sensor concerning the present invention. It is a partially broken enlarged plan view of the heater of FIG. It is a fragmentary sectional side view which shows 2nd Embodiment of this invention. It is a fragmentary sectional side view which shows 3rd Embodiment of this invention. It is a partially broken side view which shows 4th Embodiment of this invention. It is a partially broken side view which shows 5th Embodiment of this invention.

Explanation of symbols

110 ... metal shell, 120 ... outer electrode, 123, 322, 332, 362 ... electrode part,
200: cylindrical member, 320, 330, 340, 360 ... center electrode, 400 ... heater,
430 ... heating element, 500, 600 ... sealing member.

Claims (6)

A hollow electrically insulating member;
A rod-shaped discharge electrode that is fitted in the electrical insulating member and has a discharge portion on the distal end side that extends from the distal end of the electrical insulating member and discharges with other members;
In a soot sensor comprising a heating element built in the electrically insulating member,
A distance of at least 10 (mm) is provided between the heating element and the tip of the discharge electrode,
And the surface area of the discharge portion, soot sensor, characterized in that is within the range of ^{0.008 (mm 2) ~1.8 (mm} 2). A hollow electrically insulating member;
A rod-like discharge electrode that is fitted in the electrical insulating member via an annular gap and has a discharge portion that extends from the distal end of the electrical insulating member and discharges with other members on the distal end side;
In a soot sensor comprising a heating element built in the electrically insulating member,
A dense sealing member for sealing the annular gap;
Surface area of the discharge portion, soot sensor, characterized in that is within the range of ^{0.008 (mm 2) ~1.8 (mm} 2). A hollow electrically insulating member;
A rod-shaped one-side discharge electrode that is fitted in the electrical insulating member and extends from the tip of the electrical insulating member;
The other-side discharge electrode having the other-side discharge portion that faces the one-side discharge portion so as to discharge with the one-side discharge portion of the one-side discharge electrode;
In a soot sensor comprising a heating element built in the electrically insulating member,
A distance of at least 10 (mm) is provided between the heating element and the tip of the one-side discharge electrode,
And, at least one of the surface area of the respective surface area of the one-side discharge portion and the other-side discharge portion, soot, characterized in that is within the range of ^{0.008 (mm 2) ~1.8 (mm} 2) Sensor. A hollow electrically insulating member;
A rod-like one-side discharge electrode that is fitted into the electrically insulating member through an annular gap and extends from the tip of the electrically insulating member;
The other-side discharge electrode having the other-side discharge portion formed to face the one-side discharge portion so as to discharge with the one-side discharge portion of the one-side discharge electrode;
In a soot sensor comprising a heating element built in the electrically insulating member,
A dense sealing member for sealing the annular gap;
Of the surface areas of the one-side discharge part and the other-side discharge part, at least one surface area is within a range of 0.008 (mm ² ) to 1.8 (mm ² ). One of the one-side discharge electrode and the other-side discharge electrode is an anode and the other is a cathode,
The surface area of the discharge part of the anode is within a range of 0.008 (mm ² ) to 1.8 (mm ² ), and the surface area of the discharge part of the cathode is 0.07 (mm ² ) or more. The wrinkle sensor according to claim 3 or 4. Provided with a hollow metal fitting fitted with the electrical insulation member,
The one-side discharge electrode is a center electrode fitted to the electrically insulating member so as to extend from the tip thereof,
The wrinkle sensor according to any one of claims 3 to 5, wherein the other-side discharge electrode is an outer electrode extending from a tip of the metal fitting.

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