JP6386805B2 - Particulate matter detection sensor element and particulate matter detection sensor using the same - Google Patents

Description

  The present invention relates to a sensor element that detects particulate matter in a gas to be measured, and a particulate matter detection sensor including the sensor element.

  It is known that particulate matter (particulate matter: PM) such as carbon fine particles is contained in exhaust gas discharged from internal combustion engines such as gasoline engines and diesel engines. In order to collect this PM, an exhaust gas purification filter is installed in the exhaust pipe. Further, a sensor (PM detection sensor) for detecting the amount of PM contained in the exhaust gas is used downstream or upstream of the exhaust gas purification filter. As such a PM detection sensor, it is possible to detect PM in a measurement gas by attaching PM to a measurement electrode made of Pt exposed on the surface and measuring a change in electrical characteristics between the electrodes. A PM detection device has been proposed (see Patent Document 1). In addition, the PM detection device incorporates a heater for regenerating the electrode by burning and removing the PM adhering to the electrode.

JP 2011-226832 A

However, when the electrode made of Pt is repeatedly exposed to a high temperature during regeneration in an exhaust gas environment, it becomes platinum oxide (PtO ₂ ) having a low vapor pressure and may be scattered by evaporation. In particular, in the PM detection sensor, it is necessary to attach PM to the electrode at the time of detection, so that the electrode is exposed as described above, and there is a problem that the electrode made of Pt is likely to be scattered. As a result, the sensitivity of the PM detection sensor may deteriorate over time. That is, the conventional PM detection sensor has room for improvement in durability.

  The present invention has been made in view of such a background, and is intended to provide a particulate matter detection sensor element and a particulate matter detection sensor that are capable of suppressing scattering of electrodes and that have excellent durability. .

One aspect of the present invention is a sensor element for detecting particulate matter in a gas to be measured,
An insulating substrate having an attachment surface to which the particulate matter adheres;
And a particulate matter detection portion formed on the attachment surface of the insulative substrate,
The particulate matter detection unit has at least one pair of detection electrodes having different polarities and facing each other ,
Electrode surface of the sensing electrodes, Ri Contact exposed to together when being arranged such that the attachment surface flush,
The detection electrode is mainly composed of an alloy of at least one metal selected from the group consisting of Rh, Ru, Ir, and Os and Pt,
The content of the metal in the alloy is 0.5 to 50% by mass in 100% by mass of the total amount of Pt and the metal,
In the particulate matter detection sensor element, the Pt content of the alloy particles constituting the alloy is higher in the inside of the particle than in the particle surface portion of the alloy particle.

  Another aspect of the present invention is a particulate matter detection sensor comprising the particulate matter detection sensor element.

  In the PM detection sensor element, the detection electrode includes the alloy having the specific composition as a main component. In the detection electrode having such a composition, the metal component hardly evaporates even under a high temperature environment. Therefore, in the PM detection sensor element, although the detection electrode is at least partially exposed on the adhesion surface as described above, scattering of the detection electrode is suppressed. Therefore, the PM detection sensor element can maintain the sensitivity in the PM detection unit even when exposed to a high temperature environment. That is, the PM detection sensor element having the above configuration can exhibit excellent durability.

  The particulate matter detection sensor (hereinafter referred to as “PM detection sensor” as appropriate) includes a PM detection sensor element whose main component is the alloy having the specific composition described above. Therefore, scattering of the detection electrode of the PM detection sensor element is suppressed as described above, and the PM detection sensor is excellent in durability.

FIG. 3 is a perspective view of a PM detection sensor element according to the first embodiment. FIG. 3 is a development view illustrating a configuration of a PM detection element in the first embodiment. FIG. 3 is an enlarged partial cross-sectional view of a detection electrode of a PM detection sensor element in Example 1. FIG. 3 is an explanatory view showing a scanning electron micrograph of the detection electrode around the adhesion surface of the PM detection sensor element (sample X3) after the high-temperature durability test in Example 1. Explanatory drawing which shows the scanning electron micrograph of the detection electrode in the surroundings of the adhesion surface of PM detection sensor element (sample X26) after a high temperature endurance test in Example 1. FIG. Explanatory drawing which shows the modification of the formation position of the detection part in Example 1. FIG. The expanded sectional view of PM detection sensor attached in the exhaust pipe in Example 3. FIG. The perspective view of PM detection sensor element in Example 4. FIG. FIG. 6 is a development view showing a configuration of a PM detection sensor element in Example 4.

  Next, preferred embodiments of the PM detection sensor element and the PM detection sensor will be described. The PM detection sensor is used for detecting particulate matter (PM) contained in a measurement gas such as exhaust gas. The PM detection sensor can be disposed, for example, upstream and / or downstream of an exhaust gas purification filter (diesel particulate filter; DPF, gasoline particulate filter; GPF). The PM detection sensor can be applied to a diesel engine or a gasoline engine.

  As a material for the insulating substrate, for example, a ceramic material excellent in electrical insulation and heat resistance is suitable. Specifically, alumina or the like can be used as the ceramic material.

  The detection electrode has an alloy as a main component. The alloy is composed of at least one metal selected from the group consisting of Rh, Ru, Ir, and Os. It is preferable that the Pt content in the particle surface portion of the alloy particles constituting the alloy is lower than the Pt content in the particles. That is, the Pt content is preferably higher in the interior of the particle than in the particle surface portion of the alloy particle. In this case, the scattering of the detection electrode can be further prevented. Therefore, the durability of the PM detection sensor element can be further improved. From the same viewpoint, the Pt content in the alloy particles is more preferably 50% by mass or more. The Pt content in the particle surface portion and inside the particle of the alloy particles can be measured by, for example, quantitative analysis using a transmission electron microscope (TEM).

  The particle surface portion of the alloy particle is an outer peripheral portion including the surface of the alloy particle, and refers to a range from the surface to a predetermined distance inside. Specifically, for example, a range from the surface to a distance of 1/4 of the radius inward can be used as the particle surface portion of the alloy particle. The inside of the particle is a portion inside the particle surface portion. The radius of the alloy particles can be defined based on the average particle diameter. The average particle size is observed and photographed with a scanning electron microscope (FE-SEM) or the like at a predetermined magnification, and the average of the particle sizes of a predetermined number (10 or more) of alloy particles is arithmetically averaged. Can be obtained.

Example 1
In this example, a plurality of PM detection sensor elements (samples X1 to X26) having different detection electrode compositions are manufactured, and durability of these elements is evaluated. As a representative example, first, the PM detection sensor element 1 of the sample X3 will be described with reference to FIGS.

  As shown in FIGS. 1 and 2, the PM detection sensor element 1 (hereinafter referred to as “sensor element 1” as appropriate) is used to detect particulate matter (PM) in the gas to be measured. The sensor element 1 includes an insulating substrate 2 having an adhesion surface 21 to which PM adheres, and a PM detector 3 formed on the adhesion surface 21. The PM detection unit 3 is formed by at least partially exposing at least one pair of detection electrodes 31 having different polarities and facing each other on the attachment surface 21. In the sensor element 1 of the sample X3, the detection electrode 31 is mainly composed of an alloy of Pt and Rh. The content of Rh in the alloy is 2% by mass in 100% by mass of the total amount of Pt and Rh.

  As shown in FIG. 1, the insulating substrate 2 has a rectangular parallelepiped shape and is made of alumina. When the surface including the longitudinal direction (X direction) is defined as a side surface, in the sensor element 1 of the present example, one of the side surfaces is the adhesion surface 21. The PM detection unit 3 is disposed on the tip side of the adhesion surface 21 (right side in the X direction in FIG. 1). The detection unit 3 includes a plurality of detection electrodes 31 (31a, 31b, 31c, 31d, 31e) arranged in parallel at a predetermined interval. These detection electrodes 31 have alternately different polarities, and are embedded in the insulating base 2 so that the electrode surfaces are flush with the adhesion surface. In addition, the position of the adhesion surface 21 and the detection part 3 can be changed suitably. For example, as shown in FIG. 6, one of the two end faces in the longitudinal direction (X direction) of the rectangular parallelepiped insulating substrate 2 can be used as the attachment surface 21, and the detector 3 can be disposed on the attachment surface 21. is there.

  As shown in FIG. 2, the insulating base 2 is composed of a laminate of a plurality of plate-like insulating substrates 22 to 28. The detection electrodes 31a to 31e are made of electrode films formed on the surfaces of the insulating substrates 23 to 27, for example, by screen printing. As shown in FIG. 2, for example, the detection electrodes 31a to 31e can be formed by alternately arranging the electrode films 31X and 31Y formed in two types of patterns in the stacking direction. As shown in FIG. 3, each detection electrode 31 contains an alloy 311 of Pt and Rh and an aggregate 312 dispersed in the alloy 311. The aggregate 312 is made of alumina. The content of the aggregate 312 in this example is 10 parts by mass with respect to 100 parts by mass of the alloy 311.

  As shown in FIG. 2, the electrode films 31 </ b> X and 31 </ b> Y have substantially trapezoidal shapes that are symmetrical to each other, and the long sides are exposed on the adhesion surface 21 of the insulating substrates 23 to 27. The short sides of the electrode films 31X and 31Y are arranged so as to be shifted from each other, and through holes 2A and 2B penetrating the substrates 23 to 27 are formed in the vicinity of the short sides. Here, the electrode film 31X and the through hole 2A are formed in the insulating substrates 23, 25, and 27, and the electrode film 31Y and the through hole 2B are formed in the insulating substrates 24 and 26. The through hole 2A is at a position facing the electrode film 31Y and the through hole 2B is opposed to the electrode film 31X in the stacking direction. Further, an extraction electrode 311 extending from the electrode film 31X to the edge in the longitudinal direction (left edge in the figure) is screen-printed on the uppermost insulating substrate 27 among the insulating substrates 23, 25, 27 on which the electrode film 31X is formed, for example. It is formed by. In addition, a lead electrode 312 extending from the electrode film 31Y to the longitudinal edge (left edge in the drawing) is formed on the lowermost insulating substrate 24 of the insulating substrates 24 and 26 on which the electrode film 31Y is formed by, for example, screen printing. Has been.

  And the above-mentioned insulating substrates 23-27 and the insulating substrate 28 are laminated | stacked in order on the insulating substrate 22 as the lowest layer. As a result, the detection electrodes 31a, 31c, 31e (electrode film 31X) are electrically connected to each other via the conductive material filled in the through holes 2B located above and below the detection electrodes 31a, 31c, 31e, and are electrically connected to the outside by the extraction electrode 311. Connection is possible. The detection electrodes 31b and 31d (electrode film 31Y) are electrically connected to each other via a conductive material filled in the through holes 2A located above and below the detection electrodes 31b and 31d, and are electrically connected to the outside by the extraction electrode 312. It becomes possible. In addition, a heater electrode film 39 is formed on the lowermost insulating substrate 22 by, for example, screen printing, and the sensor element 1 of this example incorporates a heater.

The extraction electrodes 311 and 312 can be electrically connected to the power supply unit 37 in FIG. The lead electrodes 311 and 312 are electrically connected to a resistance measuring unit (electric characteristic measuring unit) 38, and the electric characteristics of the detecting unit 3, specifically, the resistance value between the counter electrodes of the detecting electrodes 31a to 31e are measured. Can be measured. Here, the distance between the detection electrodes 31a to 31e is constant, and the opposing detection electrode 31a and detection electrode 31b, detection electrode 31b and detection electrode 31c, detection electrode 31c and detection electrode 31d, detection electrode 31d and detection electrode 31e are ,
The polarities are different from each other. The detection electrodes 31a, 31c, and 31e having the same polarity are connected to the extraction electrode 311 and the detection electrodes 31b and 31d are connected to the extraction electrode 312. Therefore, when the adhesion surface 21 is exposed to an atmosphere containing PM, the resistance value between the counter electrodes of the detection electrodes 31a to 31e can be measured, and PM deposition can be detected from the change.

  Next, a method for manufacturing the sensor element will be described. The sensor element can be manufactured by, for example, a sheet lamination method. Specifically, first, a ceramic sheet is formed on a film using a known doctor blade method. Alumina is suitably used for the ceramic sheet material. Next, the ceramic sheet is punched in accordance with the size of each of the insulating substrates 22 to 28 (see FIG. 2), and punched to provide the through holes 2A and 2B, respectively. Here, the location and size of the through hole can be arbitrarily set.

  Next, the electrode films 31X and 31Y are printed on the ceramic sheet with the two types of patterns described above. For the formation of the electrode film, a paste-like electrode material obtained by mixing and kneading alloy particles made of a Pt—Rh alloy, an aggregate made of alumina, an organic solvent, and an organic binder is used. An electrode pattern can be formed on the ceramic sheet by screen printing this electrode material in a predetermined pattern. The alloy particles can be produced by mixing an acid solution containing Pt ions and Rh ions and performing a reduction reaction with a reducing agent. At this time, by controlling the reaction rate and the deposition rate, it is possible to deposit Pt and Rh in this order from the center of the alloy particles toward the outside. In manufacturing the sensor element of sample X3 of this example, alloy particles containing 98% by mass of Pt and 2% by mass of Rh were manufactured by adjusting the amounts of Pt ions and Rh ions.

  Furthermore, the pattern of the extraction electrodes 311 and 312 was printed by using an electrode material. A pattern of the heater electrode film 39 was printed.

  Ceramic sheets on which these patterns were printed were sequentially laminated, and the laminate was fired. Then, the detection part 3 which exposed the detection electrode 31 to the adhesion surface 21 was formed by grind | polishing the adhesion surface of PM (refer FIG. 1). In this way, the sensor element 1 (sample X3) can be obtained as shown in FIGS.

  Further, in this example, a plurality of sensor elements (sample X1, sample X2, sample X4 to sample X26) were further produced in the same manner as the sample X3 except that the composition of the alloy in the detection electrode was changed. The composition of the noble metal in the detection electrode of each sample is shown in Table 1 described later.

  Specifically, Sample X1, Sample X2, Sample X4, and Sample X5 are sensor elements manufactured in the same manner as Sample X3 described above, except that the blending ratio of Pt and Rh was changed. Samples X6 to X10 were prepared in the same manner as Sample X3 except that Ru was used instead of Rh and the compounding ratio was adjusted as shown in Table 1 described later. It is an element. Samples X11 to X15 were manufactured in the same manner as Sample X3 except that Ir was used instead of Rh and the compounding ratio was adjusted as shown in Table 1 to be described later. It is an element. Samples X16 to X20 were prepared in the same manner as Sample X3 except that Os was used instead of Rh and the blending ratio was adjusted as shown in Table 1 described later. It is an element. Samples X21 to X25 were prepared in the same manner as Sample X3 except that Pd was used instead of Rh and the blending ratio was adjusted as shown in Table 1 to be described later. It is an element. Sample X26 is a sensor element manufactured in the same manner as Sample X3 except that it was manufactured without using metal in addition to Pt.

Next, the high temperature durability test was done about the sensor element of each sample X1-X26.
Specifically, first, each sample was heated at a temperature of 900 ° C. for 250 hours. And the distance between the detection electrodes in a detection part was measured, and the change (increase) rate from the distance before a high temperature endurance test was computed. The distance between the detection electrodes before the high temperature durability test is 20 μm. And, regarding durability, when the rate of change is 0%, it is evaluated as excellent, when the rate of change exceeds 0% and 5% or less is evaluated as good, and when the rate of change exceeds 5%, it is evaluated as impossible. did. The results are shown in Table 1.

  The distance between the detection electrodes can be examined using an electron microscope. As representative examples, scanning electron microscope (SEM) photographs of the detection electrodes in the vicinity of the adhesion surface in Sample X3 and Sample X26 after the high-temperature durability test are shown in FIGS. 4 and 5, respectively. For example, in FIG. 5, the detection electrodes 31 are retracted from the adhesion surface 21, and the distance between the detection electrodes 31 is increased by the retracted distance. The receding distance L is the maximum distance among the distances from the adhesion surface 21 to the region where the alloy 311 exists. On the other hand, in the SEM photograph (see FIG. 4) of the sample X3 after the high temperature endurance test, no receding from the adhesion surface 21 of the detection electrode 31 is observed.

  As is known from Table 1, in the sample X26 having a detection electrode whose metal component is composed only of Pt, the distance between the detection electrodes was greatly increased as a result of the evaporation of Pt in the high temperature durability test. Further, in Samples X21 to X25 having detection electrodes made of an alloy of Pt and Pd, the rate of change is less than that of Sample X26, but the durability is not sufficient.

  On the other hand, in the samples X1 to X20 having an alloy of Pt and at least one metal selected from the specific group consisting of Rh, Ru, Ir, and Os, the metal component is adjusted by adjusting the compounding ratio. Transpiration was suppressed and high durability was exhibited. As is known from Table 1, the contents of Rh, Ru, Ir, and Os in a total of 100% by mass of Pt and at least one metal selected from the specific group consisting of Rh, Ru, Ir, and Os. Is preferably 0.5 to 50% by mass. More preferably, it is 2-50 mass%, More preferably, 10-50 mass% is good. As described above, by adopting an alloy of Pt and a specific noble metal as a component of the detection electrode and adjusting the composition thereof, a PM detection sensor element having excellent durability can be realized.

  In this example, the content ratio of Pt and other metals in the alloy is shown in Table 1 based on the composition at the time of manufacture, but the content ratio may be measured by analysis of the detection electrode after manufacture. it can. Specifically, it can be measured by an electron beam microanalyzer (EPMA). In this case, for example, JXA-8800 manufactured by JEOL Ltd. can be used as a measuring apparatus, and measurement can be performed under conditions of an acceleration voltage of 15 kV and a probe current of 50 nA.

  Moreover, in this example, the detection electrode 31 contains the aggregate 312 which consists of alumina 312 (refer FIG. 3). That is, the detection output electrode 31 includes a noble metal alloy 311 and an aggregate 312 dispersed therein, and the aggregate 312 is made of ceramics made of the same material as the insulating base 2. Therefore, the detection electrode 31 and the insulating substrate 2 can exhibit excellent adhesion. And the peeling of the detection electrode 31 in a high temperature environment can be suppressed.

  As shown in FIGS. 1 to 3, in this example, the detection electrode 31 is embedded in the insulating base 2, and the end of the detection electrode 31 is exposed from the adhesion surface 21 of the insulating base 2. The detection unit 3 is formed. In this case, the interval between the detection electrodes 31 can be reduced by reducing the thickness of the above-described insulating substrates 23 to 27 constituting the insulating base 2. As a result, the sensor element 1 with high detection sensitivity can be realized. On the other hand, in the sensor element 1 having such a configuration, when the metal component of the detection electrode 3 evaporates in a high temperature environment, the detection electrode 3 is not exposed to the adhesion surface 21 and PM detection in the detection unit 3 is not possible. May be possible. However, by employing the alloy composition of the detection electrode 3 in the samples X2 to X5, samples X7 to X10, X12 to X15, and X17 to X20, the transpiration of the metal component is suppressed, so that it is exposed to a high temperature environment. Even PM can be detected. That is, in the sensor element 1 having the detection portion 3 in which the end portion of the detection electrode 3 is exposed from the adhesion surface 21 of the insulating substrate 2, the merit by adopting the above specific alloy composition becomes remarkable.

(Example 2)
This example is an example of a sensor element in which the amount of aggregate in the detection electrode is changed.
That is, in this example, as shown in Table 2 described later, the amount of aggregate (alumina) with respect to the metal component in the detection electrode was changed, and a plurality of sensor elements (samples X27 to X44) were produced. The sensor element of this example has the same configuration as that of Example 1 except that the amount of alumina in the detection electrode and the composition of the metal component are changed as shown in Table 2. In addition, the quantity of the alumina in Table 2 is the quantity (mass part) with respect to 100 mass parts of noble metal alloys.

  About each sample X24-sample X44, the high temperature endurance test similar to Example 1 was done. And the distance between the detection electrodes after a high temperature endurance test was measured like Example 1, and durability was evaluated. The results are shown in Table 2.

  As is known from Table 2, the content of alumina (aggregate) in the detection electrode is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the noble metal alloy. In this case, as shown in Example 1, by adjusting the composition in the alloy, transpiration of the detection electrode is suppressed, and the sensor element can exhibit excellent durability. By adjusting the amount of the aggregate to the above range, the transpiration of the metal component can be further suppressed. Further, if the amount of aggregate is too small, the detection electrode may be peeled off in a high temperature environment, and if the amount of aggregate is too large, the PM detection sensitivity may be decreased. Also from this viewpoint, the amount of the aggregate is preferably 5 to 20 parts by mass with respect to 100 parts by mass of the noble metal alloy.

(Example 3)
Next, an example of a PM detection sensor including a sensor element will be described. As shown in FIG. 7, the PM detection sensor 4 of this example includes a cylindrical housing 40 that is screwed to an exhaust pipe 5 of an automobile, for example, and a cylindrical insulator 41 disposed inside the PM housing 4 includes an embodiment. One sensor element 1 (for example, sample X3) is inserted and fixed. The insulator 41 holds the upper part of the sensor element 1. The lower part (tip) of the sensor element 1 protrudes from the insulator 41 and the housing. The lower part of the sensor element 1 is arranged in a hollow cover 42 protruding into the exhaust pipe 5. Through holes 420 and 421 for allowing the gas 51 to be measured (exhaust gas 51) to flow in and out are formed in the bottom and sides of the cover 42.

  The PM detection sensor 4 of this example is disposed in an exhaust pipe 5 of a diesel engine or a gasoline engine. Specifically, for example, the PM detection sensor 4 can be disposed downstream of a diesel particulate filter (DPF) or a gasoline particulate filter (GPF) for collecting PM. In this case, PM that passes through the DPF or GPF can be detected by the PM detection sensor 4.

  The sensor element 1 can be arrange | positioned so that the adhesion surface 21 may face the flow direction of the to-be-measured gas 51, for example (refer FIG. 7). Then, the amount of PM contained in the measurement gas 51 can be detected by adhering to the PM detection unit 3 provided on the adhesion surface 21.

In the PM detection sensor 4 of this example, samples X2 to X5, samples X7 to X10, X12 to X15, X17 to X20 in Example 1, X29 to X32 in Example 2, samples X35 to X38, and samples X41 to X44 are used. The sensor element 1 can be used. In this case, the PM detection sensor 4 can exhibit excellent durability by taking advantage of the above-described excellent durability of the sensor element 1.
Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

(Example 4)
This example is an example of a PM detection sensor element having a comb-like electrode structure.
As shown in FIGS. 8 and 9, the PM detection sensor element 1 of this example includes a rectangular parallelepiped insulating substrate 2 having a PM adhesion surface 21 and a PM detection unit 3 formed on the adhesion surface. The insulating substrate 2 is made of alumina. The PM detection unit 3 is provided in a recess 29 formed on the surface of the insulating substrate 2. The detection unit 3 includes a plurality of detection electrodes 31 (31f, 31g, 31h, 31i, 31j, 31k, 31l, and 31m) arranged in parallel at a predetermined interval. These detection electrodes 31 have different polarities alternately.

  As shown in FIG. 9, the insulating base 2 is composed of a laminate of a plurality of plate-like insulating substrates 200, 201, 202. The detection electrodes 31f to 31m are made of an electrode film formed, for example, by screen printing on the surface of the insulating substrate 201 disposed in the middle. The electrode film in this example includes a pair of counter electrodes 34 and 35. The counter electrodes 34 and 35 have extraction electrodes 340 and 350 extending in the longitudinal direction, and each of the plurality of detection electrodes 31 extending in a direction orthogonal to the longitudinal direction. The counter electrodes 34 and 35 are arranged so that the extraction electrodes 340 and 350 face each other, and the other detection electrode 31 enters between the one detection electrodes 31.

  In addition, a heater electrode film 39 is formed on the lowermost insulating substrate 200 by, for example, screen printing, and the PM detection sensor element 1 of this example incorporates a heater. A through-hole 290 is provided in the insulating substrate 202 which is the uppermost layer. In the laminated body of each insulating substrate 200, 201, 202, the detection electrode 31 arranged in a comb-tooth shape is partially exposed at the through-hole 290.

  The PM detection sensor element 1 of this example can be manufactured in the same manner as in Example 1 except that the electrode formation pattern is changed and the shape and number of used ceramic sheets are changed. The detailed explanation of is omitted.

  Also in the PM detection sensor element 1 of the present example, by adopting the detection electrode 31 made of an alloy composition exhibiting excellent durability in Examples 1 and 2, the same effects as those of Example 1 and Example 2 are obtained. Can be obtained. That is, even in a high temperature environment, the detection electrode 31 is less likely to be scattered, and excellent durability can be exhibited.

DESCRIPTION OF SYMBOLS 1 PM detection sensor element 2 Insulating base | substrate 21 Adhesion surface 3 PM detection part 31 Detection electrode

Claims (5)

A sensor element (1) for detecting particulate matter in a gas to be measured,
An insulating substrate (2) having an attachment surface (21) to which the particulate matter adheres;
A insulative substrate (2) above attachment surface (21) which is formed in the particulate matter detecting portion of the (3),
The particulate matter detection unit (3) has at least one pair of detection electrodes (31) having different polarities and facing each other ,
Electrode surface of the detection electrode (31), Ri Contact exposed to together when being arranged such that the attachment surface (21) flush,
The detection electrode (3 1 ) is mainly composed of an alloy (311) of at least one metal selected from the group consisting of Rh, Ru, Ir, and Os and Pt,
The content of the metal in the alloy (311) is 0.5 to 50% by mass in 100% by mass of the total amount of Pt and the metal,
The particulate matter detection sensor element (1) characterized in that the Pt content of the alloy particles constituting the alloy (311) is higher in the interior of the particle than in the particle surface portion of the alloy particle. The particle according to claim 1, wherein the detection electrode (31) is embedded in the insulating base (2) so that the electrode surface is flush with the adhesion surface (21). A substance detection sensor element (1). The detection electrode (32) includes the alloy (311) and an aggregate (312) dispersed in the alloy (311), and the aggregate (312) includes the insulating base (2). The particulate matter detection sensor element (1) according to claim 1 or 2 , wherein the particulate matter detection sensor element (1) is made of ceramics of the same material. The particulate matter detection sensor element (1) according to claim 3 , wherein the content of the aggregate (312) is 5 to 20 parts by mass with respect to 100 parts by mass of the alloy. A particulate matter detection sensor (4) comprising the particulate matter detection sensor element (1) according to any one of claims 1 to 4 .