JP6488352B2 - Particulate matter detection element - Google Patents

Description

  The present invention relates to a particulate matter detection element that is suitably used for, for example, an exhaust purification system of an internal combustion engine for a vehicle and detects particulate matter present in exhaust gas that is a gas to be measured.

  A pair of electrodes is formed on the surface of an insulating substrate, and the particulate matter accumulates between the pair of electrodes by utilizing the conductivity of the particulate matter. Various types of particulate matter detection sensors that detect particulate matter in a gas to be measured such as combustion exhaust gas of an internal combustion engine from changes in electric characteristics such as capacity have been proposed.

Patent Document 1 discloses a sensor element in which a pair of comb-shaped electrodes are formed on an insulating substrate such as alumina ceramics.
In the sensor element of Patent Document 1, a voltage is applied between the pair of electrodes from the power supply unit to form a non-uniform electric field in the space between the interdigitated electrodes, and is included in the exhaust gas passing through the sensor element. The soot deposition amount can be measured by attracting soot particles to the electrode and depositing them, and detecting the interelectrode resistance at this time.

On the other hand, in Patent Document 2, conductor layers and insulating layers are alternately stacked by thick film printing and green sheets in order to accurately form the distance between the electrodes, which is difficult in conventional thick film printing, to 50 μm or less. A resistance measuring electrode for a sensor having a laminated structure and using a conductor layer as an electrode using this cross section is disclosed, and it is disclosed that the distance between the electrodes can be reduced to about 10 μm determined by the film thickness of the insulating layer.
Japanese translation of PCT publication No. 2008-502892 JP-A-60-196659

However, the conductor layers and insulating layers as described in Patent Document 2 are alternately stacked to form a laminated structure, and the conductor layers exposed in the cross section are used as a pair of electrodes. When a voltage is applied to form an electric field to deposit particulate matter between the electrodes, charge concentration occurs at the corners of the electrode ends.
For this reason, it has been found that local particulate matter is likely to be deposited near the electrode end portion where the electric field strength is high, and the individual difference of the insensitive mass may be increased, leading to a decrease in detection accuracy.

  Therefore, in view of such a situation, the present invention has a laminated structure in which a flat conductor layer and a flat insulating layer are alternately stacked to form a detection unit with the conductor layer exposed in the cross section as a pair of electrodes. An object of the particulate matter detection element is to provide a particulate matter detection element in which the shape of the end portion of the electrode layer has a characteristic shape and electric field concentration on the end portion of the electrode layer is suppressed.

The particulate matter detection element (10 , 10a, 10c, 10d, 10f ) of the present invention is
Laminate in which flat conductor layers ( 11, 11a, 11c, 11d, 11f , 12 , 12a , 12c, 12d, 12f ) and flat insulating layers (100 , 100a , 100c, 100d, 100f ) are alternately stacked. Has a structure,
Using this cross section, a detection unit (13 , 13a , 13c, 13d, 13f ) having the conductor layer as a pair of detection electrodes having different polarities is configured,
A particulate matter detection element for detecting an electrical property that varies depending on the amount of particulate matter deposited on the detection unit and detecting particulate matter in a gas to be measured,
The conductor layer has a constant film thickness and a conductor layer plane portion (110 , 110a , 110c, 110d, 110f , 120 , 120a , 120c, 120d, 120f ) having a strip-shaped cross section,
The conductor layer flat surface portion in at least one of the conductor layers has a shape that protrudes outward in the longitudinal direction at the end portion in the longitudinal direction of the strip shape, and a conductor layer edge portion that serves as an electric field concentration suppressing portion ( 111,111a, 111c, 111d, 111f, 121,121a, 121c, 121d, are provided with a 121f),
The conductor layer edges (111,111a, 111c, 111d, 111f , 121,121a, 121c, 121d, 121f) is characterized by polygonal der Rukoto having three or more corners.

  According to the present invention, the electric field concentration at the edge portion of the conductor layer is suppressed, the insensitive mass fluctuation due to the local accumulation of the particulate material on the electric field concentration portion is suppressed, and the particulate material with stable detection accuracy A detection element can be realized.

The block diagram which shows the whole outline | summary of the particulate matter detection sensor 1 in 1st Embodiment of this invention. FIG. 1B is an enlarged perspective view of a detection unit 13 that is a main part of a particulate matter detection element 10 used in the particulate matter detection sensor 1 of FIG. 1A. FIG. 1B is a developed perspective view showing an example of the internal structure of a particulate matter detection element 10 used in the particulate matter detection sensor 1 of FIG. 1A. The principal part enlarged view of the conventional particulate matter detection element 10z which the electrode layer end surface shown as the comparative example 1 is square shape. The principal part enlarged view of the particulate matter detection element 10 whose electrode layer end surface shown as Example 1 of this invention is an obtuse triangle shape. The principal part enlarged view of the particulate-material detection element 10a whose electrode layer end surface shown as Example 2 of this invention is an acute angle triangle shape. The principal part enlarged view of the particulate matter detection element 10b whose electrode layer end surface shown as the reference example 3 of this invention is circular arc shape. The principal part enlarged view of the conventional particulate matter detection element 10y which the electrode layer end surface shown as the comparative example 2 is square shape, and the position of an end surface is not constant. The electrode layer end surface shown as Example 4 of this invention is an obtuse triangle shape, and the principal part enlarged view of the particulate matter detection element 10c where the position of an end surface is not constant. The electrode layer end surface shown as Example 5 of this invention is an acute angle triangle shape, and the principal part enlarged view of 10 d of particulate matter detection elements with which the position of an end surface is not constant. The electrode layer end surface shown as the reference example 6 of this invention is circular arc shape, and the position of an end surface is a principal part enlarged view of the particulate matter detection element 10e. The schematic diagram which shows the electric field strength distribution of the detection part plane in the comparative example 1. FIG. FIG. 3 is a schematic diagram illustrating an electric field intensity distribution on a detection unit plane according to the first embodiment. FIG. 6 is a schematic diagram showing an electric field intensity distribution on a detection unit plane in Example 2. FIG. 9 is a schematic diagram showing an electric field intensity distribution on a detection unit plane in Reference Example 3. The schematic diagram which shows the electric field strength distribution of the detection part plane in the comparative example 2. FIG. FIG. 9 is a schematic diagram showing an electric field intensity distribution on a detection unit plane in Example 4. FIG. 10 is a schematic diagram illustrating an electric field intensity distribution on a detection unit plane in Example 5. FIG. 10 is a schematic diagram showing an electric field intensity distribution on a detection unit plane in Reference Example 6. The principal part expansion perspective view which shows the outline | summary of the detection part 13f in Example 7. FIG. The characteristic view which shows the change of the sensor output of Example 1 with the comparative example 1. FIG. The characteristic view which shows the effect with respect to the variation reduction of the dead mass of this invention with a some comparative example. The schematic diagram which shows the outline | summary of the manufacturing process of the comparative example 1. FIG. The schematic diagram which shows the outline | summary of the manufacturing process of the comparative example 3. FIG. The schematic diagram which shows the outline | summary of the manufacturing process of Example 1 of this invention. The schematic diagram which shows the outline | summary of the manufacturing process of Example 2 of this invention. The top view which shows the outline | summary of the screen for thick film printing used in manufacture of the particulate matter detection element of this invention. FIG. 9B is a cross-sectional view and a plan view of an insulating layer formed with a conductor layer corresponding to a cross-sectional view along BB in FIG. 9A. The top view which shows the modification of the screen for thick film printing used for this invention.

With reference to FIG. 1A, FIG. 1B, and FIG. 1C, the outline | summary of the particulate matter detection sensor 1 in 1st Embodiment of this invention and the particulate matter detection element 10 which is the principal part of this invention is demonstrated.
The particulate matter detection sensor 1 (hereinafter referred to as the sensor 1) of the present invention is, for example, a particulate form in which combustion exhaust from an internal combustion engine is used as a measurement gas and a detection unit 13 provided in the measurement gas is provided. The material detection element 10 (hereinafter, abbreviated as the element 10), the power source 2 that applies a predetermined voltage to the element 10, and the electrical characteristics such as the current flowing through the element 10, the change in voltage, and the change in impedance are measured. The measuring unit 3 detects particulate matter in the gas to be measured.

It is possible to detect the particulate matter in the gas to be measured by measuring the electrical characteristics that change depending on the amount of the particulate matter deposited on the detection unit 13 of the element 10 by the measurement unit 3.
In the following description, the side where the detection unit 13 of the element 10 is provided and exposed to the gas to be measured is referred to as the distal end side, and the side connected to the power supply unit 2 and the measurement unit 3 is referred to as the proximal end side.

The sensor 1 is installed downstream of the DPF and can be used for detecting an abnormality of the DPF. Alternatively, it can be used in a system that is installed upstream of the DPF and directly detects the particulate matter PM flowing into the DPF.
Note that, when actually arranged in the gas flow path to be measured, in order to fix the element 10, it is generally used as a particulate matter detection sensor such as a housing not shown or a cover body that protects the detection unit 13. A known configuration can be adopted as appropriate.

With reference to FIG. 1B, the characteristic of the element 10 which is the principal part of this invention is explained in full detail.
The element 10 has a laminated structure in which flat conductor layers 11 and 12 and flat insulating layers 100 are alternately stacked.
The element 10 constitutes a detection unit 13 using the cross sections of the conductor layers 11 and 12 as a pair of detection electrodes having different polarities.

As illustrated in FIG. 1B, the detection unit 13 includes a pair of conductor layers 11 and 12 arranged alternately with the insulating layer 100 interposed therebetween.
In the present embodiment, the conductor layers 11 and 12 have a constant film thickness and have conductor layer plane portions 110 and 120 (hereinafter, abbreviated as plane portions 110 and 120) having a strip-shaped cross section. The planar portions 110 and 120 in at least one of the conductor layers 11 and 12 are strip-shaped longitudinal end portions that are convex outward in the longitudinal direction and serve as electric field concentration suppressing portions. 111, 121 (hereinafter abbreviated as edge portions 111, 121). Here, the conductor layer edges having a triangular cross-section tapering on both sides of the conductor layer plane portions 110, 120 are provided. Parts 111 and 121 (hereinafter abbreviated as edge parts 111 and 121).
In the present invention, the shape that protrudes outward in the longitudinal direction specifically includes a polygonal shape having three or more corners. For example, by providing conductor layer edge portions 111 and 121 formed in a triangular cross section at both ends of the conductor layers 11 and 12, electric field concentration at the edges of the conductor layers 11 and 12 is suppressed, It is intended to prevent local particulate matter from accumulating on the concentrated part and improve and stabilize detection accuracy.

The conductor layers 11 and 12 are made of a metal material such as aluminum, gold, platinum, or tungsten, or a metal oxide material such as ruthenium oxide, or LNF (LaNi _0.6 Fe _0.4 O ₃ ) or LSN (LaNi). _0.6 Fe _0.4 O ₃ ), LSM (La _1-X Sr _X MnO _3-δ ), LSC (La _1-X Sr _X CoO _3-δ ), LCC (La _1-X Ca _X CrO _{3- δ} ), LSCN (La _0.85 Sr _0.15 Cr _1-X Ni _X O _3-δ ) (0.1 ≦ X ≦ 0.7), etc. Any known conductive material can be used as appropriate.
The insulating layer 100 includes an insulating layer material such as alumina, magnesia, titania, mullite, a dielectric material obtained by mixing a high dielectric constant material such as barium titanate having a high dielectric constant with alumina or zirconia, or 8YSZ (ZrO ₂ ). A known ceramic material such as partially stabilized zirconia typified by _0.82 (Y ₂ O ₃ ) _0.08 ) can be used as appropriate.

In addition, in this embodiment, the example which formed the detection part 13 by exposing the cross section of a pair of conductor layers 11 and 12 to the side surface direction of the front end side of the particulate matter detection element 10 formed in the rectangular parallelepiped shape is shown. However, the detection unit 13 may be provided by exposing the cross section of the pair of conductor layers 11 and 12 from the bottom surface on the tip side of the element 10.
Further, in FIGS. 1A to 1C, a pair of conductor layers 11 and 12 are alternately stacked, and in order to clarify that the polarities are alternately different, different hatching is applied. 11 and 12 are not distinguished from each other.

A more specific internal structure of the element 10 will be described with reference to FIG. 1C.
The insulating layer 100 is formed in a flat plate shape by a known manufacturing method such as a doctor blade method, and through holes are formed at predetermined positions as necessary to form through hole electrodes 114 and 124.
The pair of conductor layers 11 and 12 are formed by plane portions 110 and 120 provided with end edge portions 111 and 121 by a manufacturing method described later, lead portions 112 and 122, terminal portions 113 and 123, and through-holes for connection to the outside. The electrodes 114, 124, and 125 are configured.
The through-hole electrodes 114 and 124 are designed to conduct the flat portions 110 and 120 having the same polarity.
The lead portions 112 and 122, the through-hole electrodes 114 and 124, and the terminal portions 113 and 123 are formed by a known manufacturing method such as thick film printing.

The insulating layer 100 has a laminated structure in which conductor layers 11 and 12 are alternately stacked, and in this embodiment, the lowermost insulating layer 100H includes a heating element 140 that generates heat when energized, A pair of lead portions 141 and terminal portions 142 that are connected to the heating element 140 are formed to constitute the heating portion 14.
A known resistance heating material such as tungsten, molybdenum silicite or ruthenium oxide is used for the heating element 140, and a known conductive metal material such as gold, platinum or tungsten is used for the lead portion 141 and the terminal portion 142. And formed by a known method such as thick film printing.
The element 10 is integrated by firing.
In addition, the detection unit 13 in the present embodiment is formed by performing a lamination and firing process, and then appropriately cutting and polishing so that a cross section is exposed on the side surface of the element 10.

Here, with reference to FIGS. 2A, 2B, 2C, 2D, 3A, 3B, 3C, and 3D, Comparative Example 1 and Example 1 were examined to confirm the effects of the present invention. Example 2, Reference Example 3, Comparative Example 2, Example 4, Example 5, and Reference Example 6 will be described.
In both the comparative example and the example, the basic structure is the same as the laminated structure of the example 1 shown in FIG. 1c. The numbers z and y are assigned as branch numbers, and Examples 2 , 4, 5, and Reference Examples 3 and 6 are assigned branch numbers a to f, respectively. Further, the comparative example 3 described later is distinguished by assigning a symbol x as a branch number, and the examples 7 and 8 by branch numbers f and g, respectively.

In the element 10z shown in FIG. 2A as Comparative Example 1, insulating layers 100z, conductor layers 11z (plane portions 110z), and conductor layers 12z (plane portions 120z) are alternately stacked.
The conductor layers 11z and 12z of Comparative Example 1 have a rectangular cross section, a square end surface, and the end surfaces are aligned.

In the element 10 shown in FIG. 2B as Example 1, the insulating layers 100, the conductor layers 11, and the conductor layers 12 are alternately laminated.
Edge sides 111 and 121 having a tapered triangular shape (obtuse angle) are formed on both sides of the flat portions 110 and 120 of the conductor layers 11 and 12 of the first embodiment. The positions of the parts 111 and 121 are aligned.
The edge portions 111 and 121 have at least three corner portions, and in the strip-shaped cross section of the conductor layers 11 and 12, the corner portions having smaller angles outside the corner portions located on the sides in the longitudinal direction. It has the shape which has at least one. For example, corners with smaller angles are formed on two sides in the short direction, and the edge portions 111 and 121 having a shape protruding outward are formed.

The element 10a shown in FIG. 2C as Example 2 is different from Example 1 in that the edge portions 111a and 121a of the conductor layers 11a and 12a have an acute triangular cross section.
The element 10b shown in FIG. 2D as Reference Example 3 is different from Example 1 in that the edge portions 111b and 121b have a circular arc-shaped cross section. The conductor layers 11b and 12b have a constant film thickness and have a strip-shaped conductor layer flat surface portion 110b and 120b, and are formed on both sides of the conductor layer flat surface portion 110b and 120b so as to protrude outward in the longitudinal direction. As an example of the shape having no corners, the conductor layer edge portions 111b and 121b having a circular arc shape that is smoothly curved are provided.

The element 10y shown in FIG. 3A as the comparative example 2 is different from the comparative example 1 in that the conductor layers 11y and 12y (plane portions 110y and 120y) have square end faces, but the end face positions are not aligned. .
The element 10c shown in FIG. 3B as the fourth embodiment is similar to the first embodiment in that the edge portion 111c has a tapered triangular shape (obtuse angle) on both sides of the flat portions 110c and 120c of the conductor layers 11c and 12c. 121c are formed, but the positions of the edge portions 111c and 121c are not aligned in the stacking direction.

The element 10d shown in FIG. 3C as the fifth embodiment is similar to the second embodiment in that the edge portion 111d has a tapered (acute angle) cross section on both sides of the flat portions 110d and 120d of the conductor layers 11d and 12d. , 121d, but the positions of the edge portions 111d, 121d are not aligned in the stacking direction.
The element 10e shown in FIG. 3D as Reference Example 6 has an arc-shaped cross section in which the edge portions 111e and 121e on both sides of the flat surface portions 110e and 120e are curved in the conductor layers 11e and 12e, as in Reference Example 3. However, the difference is that the positions of the edge portions 111e and 121e are not aligned in the stacking direction.

Here, referring to FIGS. 4A, 4B, 4C, 4D, 5A, 5B, 5C, and 5D, it is generated on the plane of the detection unit when a certain voltage is applied between a pair of conductor layers. Differences in simulation results in Comparative Example 1, Example 1 , 2, Reference Example 3, Comparative Example 2, Examples 4 , 5, and Reference Example 6 will be described.
As shown in FIG. 4A, in Comparative Example 1, a strong electric field concentration occurs at the corners of the conductor layers 11z and 12z, and the electric field strength in the region where the electric field strength between the pair of plane portions 110z and 120z is uniform is relatively high. Turned out to be lower.
As shown in FIG. 4B, in the first embodiment, the electric field concentration portions are dispersed at the three portions of the edge portions 111 and 121, and the ratio of the electric field concentration becomes relatively low, and the flat portions 110 and 120 correspondingly. It was found that the charge intensity in the region where the electric field intensity becomes uniform becomes relatively high.

As shown in FIG. 4C, it was found that in Example 2, the electric field concentration was further suppressed, and the charge intensity in the region where the electric field intensity between the flat portions 110a and 120a became uniform was the highest.
As shown in FIG. 4D, it was found that the charge intensity in the region in which the electric field concentration is suppressed and the electric field intensity between the flat portions 110b and 120b is uniform is also relatively high in the reference example 3.

  Next, looking at the case where the end face positions are not aligned, as shown in FIG. 5A, in Comparative Example 2, the electric field concentration is suppressed more than in Comparative Example 1, and the electric field strength between the pair of flat portions 110y and 120y becomes uniform. It was found that the electric field strength in the region was relatively higher than that of Comparative Example 1.

On the other hand, in Examples 4 and 5, the electric field concentration in the region where the electric field concentration between the pair of plane portions 110c, 110d, 120c, and 120d is uniform due to the concentration of charges is different from that in Examples 1 and 2. 2 was found to be relatively lower.
However, in Reference Example 6, than Reference Example 3, the electric field concentration can be suppressed, a pair of flat portions 110e, the electric field strength in the region where the electric field intensity becomes uniform among 120e, from Example 3, relatively high It has been found.

Here, with reference to FIG. 6, the element 10f in Example 7 of this invention is demonstrated.
In the present embodiment, in the detection unit 13f, glass, alumina, or the like is used so as to cover a region where the electric field strength is nonuniform in all of the edge portions 111f and 121f and part of the flat portions 110f and 120f. A shielding layer 14 made of a known insulating material or the same material as the insulating layer 100 is provided.
In addition, the structure which provides the shielding layer 14 can be employ | adopted in any of the above-mentioned Example 1 , 2, 4, 5 and the reference examples 3 and 6. FIG.

Here, with reference to FIG. 7A and FIG. 7B, the test result performed for confirmation of the effect of this invention is demonstrated.
When the detection unit 13 of the element 10 is exposed in the gas flow path to be measured and a predetermined voltage is applied from the power supply unit 2 to flow a known amount of particulate matter, a certain amount or more of particles are supplied to the detection unit 13. There is a dead mass Q0 (dead period) in which particulate matter cannot be detected until the particulate matter is deposited.
Therefore, in addition to the above-described Comparative Example 1, Comparative Example 2, Example 1 , 2, 4, 5, 7 and Reference Examples 3 and 6 , a comparison was made by forming a conductor layer similar to Comparative Example 1 without providing an intermediate layer. When Example 3 and Comparative Example 4 in which Comparative Example 2 was provided with the aforementioned shielding layer 14 and Example 8 in which Reference Example 6 was provided with the shielding layer 14 were charged with a known amount of particulate matter, A plurality of samples were prepared for each of the comparative examples, and the dead mass Q0 until the particulate matter was detected was measured. As illustrated in FIGS. 3D and 6, the element 10g according to the eighth embodiment includes the planar portions 110g and 120g and the edge portions 111g and 121g on the conductor layers 11g and 12g.

As shown in FIG. 7A, in Comparative Example 1, it was found that the average value μ ₂ of the dead mass Q 0 is small and particulate matter can be detected at an early stage, but the variation σ ₂ between samples is large.
On the other hand, in Example 1, the average value μ ₁ of the dead mass Q0 was larger than the dead mass of Comparative Example 1, but it was found that the variation σ ₁ between samples was much smaller.
In Comparative Example 1, a strong electric field concentration occurs at the corners of the end faces of the conductor layers 11z and 12z, and the particulate matter is attracted to the electric charges collected on the surfaces and deposited locally. It is assumed that it is formed.

However, the electric field concentration at the corners is considered to be unstable due to large fluctuations between samples.
Therefore, the coefficient of variation CV (100√σ2 / μ) (%) is calculated to evaluate each sample, and the result is shown in FIG. 7B.
In Comparative Example 2, the variation is smaller than in Comparative Example 1, but all of Examples 1 , 2, 4, 5, 7 and Reference Examples 3 and 6 have a coefficient of variation more than that of Comparative Examples 1 to 4. It can be seen that the present invention has the effect of improving the reliability of the sensor.

Electric field concentration is provided by providing edge portions 111, 121, 111a, 121a, 111b, 121b, 111c, 121c, 111d, 121d, 111e, and 121e having a triangular or arcuate cross section on both end faces of the conductor layers 11 and 12. It is considered that local deposition of particulate matter on the ends of the conductor layers 11 and 12 is suppressed.
In addition, since the edge portions 111a and 121a have an acute triangular shape in cross section, the distance between the vertices where electric field concentration is likely to occur is increased, so that a conduction path is formed between the pair of edge portions 111a and 121a. It is assumed that the time to complete will be longer.

Here, with reference to FIG. 8A, FIG. 8B, FIG. 8C, and FIG. 8D, the particulate matter detection elements 10z, 10y, 10 shown as the above-described Comparative Example 1, Comparative Example 2, Example 1, and Example 2, respectively. Each manufacturing method of 10a will be described.
Comparative Example 1 shows a basic manufacturing method of the particulate matter detection element 10z in which the conductor layers 11z and 12z and the insulating layer 100z are alternately stacked and the cross section is used as the detection unit 13z.

An insulating material such as alumina is mixed with a known binder, plasticizer, dispersant, solvent, etc. and stirred to form a slurry, which is formed into a sheet by a known manufacturing method such as a doctor blade method, and has an insulating property. A sheet 100zGS is obtained.
In the punching process P0z (not shown), a guide for printing alignment and through-hole electrodes 114z and 124z for connecting conductor layers having the same polarity are embedded in advance using a mold or the like. A through hole or the like for drilling is formed as necessary, and punched into a predetermined outer shape.

In the printing process P1z as the thick film printing process, the conductive paste is discharged from the thick film printing screen on which a predetermined conductive pattern is formed, and the conductive layer printed films 11zPRT and 12zPRT are transferred to the insulating layer sheet 100zGS.
At this time, as shown enlarged in a circle, the film thickness near the center becomes thin and the film thickness near the outer periphery becomes thick due to the influence of the rheological characteristics and surface tension of the paste.

In Comparative Example 1, a paste containing the same material as the insulating material constituting the insulating layer 100 is used to cover a portion other than the conductor layer by thick film printing with the same film thickness as the conductor layer printed films 11zPRT and 12zPRT. An intermediate layer 101z is formed.
In the subsequent laminating and pressing step P2z, the insulating layer sheets 100zGS are stacked so that the polarities of the conductor layer printed films 11zPRT and 12zPRT are alternately switched, and are pressed using a mold or the like.

In the firing process P3z, the insulating layers 11z and 12z and the conductor layer 100z are simultaneously fired and integrated into the laminated structure thus obtained.
Thereafter, the element 10z is completed by exposing the cross-sections of the conductor layers 11z and 12z by cutting, polishing, or the like to form the detection unit 13z.

In Comparative Example 1, since the intermediate layer 101z is provided, there is almost no deformation of the conductor layer printed films 11zPRT, 12zPRT and the insulating layer sheet 110z at the time of laminating and pressing, and the mechanical strength of the element 10z is excellent. 11z and 12z maintain the shape of a strip-shaped cross section.
However, it has been found that when a voltage is applied between the two conductor layers, the electric field concentration at the corners is large, and the variation in dead mass is large as described above.
In addition, the element 10y shown as the comparative example 2 is based on the manufacturing method similar to the comparative example 1, and is laminated by intentionally shifting the positions of the end surfaces of the conductor layers 11y and 12y in the lamination pressing process.

With reference to FIG. 8B, the outline of the manufacturing process of the element 10x shown as the comparative example 3 and the problems of the comparative example 3 will be described.
In Comparative Example 3, as shown in the printing process P1x, only the conductor layers 110x and 120x are printed on the insulating layer sheet 100xGS punched into a predetermined shape, and the process proceeds to the lamination pressing process P2x without providing an intermediate layer.

In the lamination pressure bonding step P2x, the conductor layer printed films 11xPRT and 12xPRT are harder than the insulating layer sheet 100xGS. Therefore, at the time of laminated pressure bonding, the insulating layer sheet 100xGS is elastically deformed, and the conductor layer printed films 11xPRT and 12xPRT are changed to the insulating layer sheet 100xGS. The insulating layer sheets 100xGS are in close contact with each other so as to be recessed.
At this time, voids having a triangular cross-section are formed on both sides of the conductor layer printed films 11xPRT and 12xPRT as shown in an enlarged manner in the circle of the lamination pressure bonding step P2x in FIG. 8B.

Subsequent firing step P3x allows sintering to reduce the surface area of the voids, so the voids are reduced, but they do not disappear completely, but remain as voids or trigger delamination. There is a fear.
Moreover, the end surfaces of the conductor layers 11x and 12x after firing have polygonal or irregular shapes, and electric field concentration is likely to occur at the corners as in Comparative Example 2 described above.

With reference to FIG. 8C, the outline | summary of the manufacturing process of Example 1 of this invention is demonstrated.
In the present embodiment, a punching process in which a guide for positioning and a through hole as necessary are formed in the formed insulating layer sheet 100GS by a process similar to that of Comparative Example 1, and punched into a predetermined outer shape. At P0, at the same time as the punching of the insulating layer sheet 100GS, a concave sheet 100PCD provided with a concave portion 101 that matches the shape of the predetermined conductor layer edge portions 111 and 121 in accordance with the position where the conductor layers 11 and 12 are printed and formed. Form.
Specifically, a protrusion for forming the recess 101 is provided on the punching die, and the surface of the insulating layer sheet 100GS is pressed.
Thereby, the taper surface which inclines at a desired angle in the part which forms the conductor layer edge parts 111 and 121 can be formed.

As a result, even if normal thick film printing is performed in the printing process P1, the sides of the conductor layer edge portions 111 and 121 that are in contact with the insulating layer sheet 100GS are inclined along the shape of the recess 101.
Moreover, since the recessed part 101 is formed also in the lower surface side of the recessed sheet 100PCD, when it accumulates in the lamination | stacking crimping | compression-bonding process P1, adhesiveness with the conductor layer printed films 110 and 120 improves, and it is like Comparative Example 2. No voids are formed.

Furthermore, the insulating layer sheets 100GS can be easily brought into close contact with each other without providing an intermediate layer as used in Comparative Example 1.
As a result, when the conductor layers 11 and 12 and the insulating layer 100 are integrated by the firing step P3, the element 10 that hardly causes delamination can be formed.
In addition, since the conductor layer edge portions 111 and 121 can be formed in a triangular shape having a tapered cross section, it is easy to realize the element 10 in which electric field concentration is suppressed.

With reference to FIG. 8D, the outline | summary of the manufacturing process of Example 2 of this invention is demonstrated.
In the conductor printing process P1a in the present embodiment, when the conductor layers 11 and 12 are printed and formed on the insulating layer sheet 100 (GS), the mesh opening ratio is partially changed to reduce the printed film thickness at a predetermined position. This is different from the above-described embodiment in that the aperture ratio partial change printing screens PPM and PPMA set as described above are used.
The aperture ratio partial change printing screens PPM and PPMA will be described later with reference to FIGS. 9A, 9B, and 10. FIG.
In the present embodiment, by using the aperture ratio partial change printing screen PPM, the amount of the conductive paste discharged from the portion where the opening efficiency is set low is suppressed, and the thickness of the conductive layer formed thereby is reduced. It is possible to form the conductor layer edge portions 111a and 121a having a triangular cross section which is tapered outward and has an acute inclined surface.

Thus, the conductor layers 11a and 12a are insulated by pressure-bonding the insulating layer sheet 100GS formed with the conductor layers 11a and 12a having the conductor layer edge portions 111a and 121a having a triangular cross section using a stacked mold or the like. The conductor layers 100GS are in close contact with each other while sinking into the layer 100GS.
At this time, since the conductor layer edge portions 111a and 121a have a tapered triangular shape, a gap as shown in Comparative Example 2 is not formed.
By firing the laminated structure thus completed in the firing step P3a, the element 10a in which the electric field concentration near the conductor end face is suppressed can be formed very easily.

With reference to FIG. 9A and FIG. 9B, the characteristics of the thick film printing screen M used in the production of the particulate matter detection element 10 of the present invention, and the conductor layers 11 and 12 formed when this is used. The shape will be described.
In this figure, only the pattern that forms one conductor plane portion 110 and conductor layer edge portion 111 of the pair of conductor layers 11 and 12 is shown, but the other conductor plane portion 120, conductor layer is shown. Since the end edge portion 121 is a pattern obtained by horizontally inverting one of the patterns, the other is omitted, and the common configurations are described by arranging the reference numerals as 110/120.

In this embodiment, a part of a thick film printing screen generally used for thick film printing is rolled and partially flattened to reduce the mesh thickness and reduce the mesh opening ratio. A drop screen M is used.
The resist film R is formed in a predetermined printing pattern by applying an emulsion on a printing screen and exposing and curing a pattern in accordance with the shape of the conductor layer plane portions 110 and 120, as in general thick film printing. ing.
As shown in FIGS. 9A and 9B, the thickness of the mask M2 in the cross-sectional direction of the portion where the conductor layer edge portions 111 and 121 are printed is thin and the line width in the plane direction is wide. The aperture ratios of the portions where the edges 111 and 121 are formed by printing, that is, the opening ratios P ₁₁₁ and P ₁₂₁ for forming the edge portions are the aperture ratios of the mask M1 of the portion where the conductor plane portions 110 are formed, that is, the plane portion formation. The utilization efficiency P ₁₁₁ is lower than P ₁₂₁ .
For this reason, as shown in FIG. 9B, when the conductor layer plane portions 110 and 120 are printed and formed, the amount of paste discharged from the mask M2 is reduced, and the film thickness of the conductor layer edge portions 111 and 121 is determined as follows. It becomes thinner than the film thickness of the flat portions 110 and 120.

With reference to FIG. 10, a modification MA of the aperture ratio partial lowering screen will be described.
In the above-described embodiment, the aperture ratio partial lowering screen M in which a part of the thick film printing screen is pressurized to reduce the aperture ratio has been shown as an example. However, as shown in FIG. Then, the edge portion opening ratio P is increased by increasing the weaving density of the weft and warp of the mask M2A for printing the conductor layer edge portions 111 and 121 as compared to the mask M1A for printing the conductor layer flat portions 110 and 120. ₁₁₁ A / P ₁₂₁ A is lower than the flat surface portion forming aperture ratio P ₁₁₀ A / P ₁₂₀ A In the aperture ratio partial decrease screen MA in the present embodiment, a screen mesh whose opening efficiency is partially adjusted in advance is used. A resist R is formed so as to have a predetermined conductor pattern.

Thus, when the conductor layers 11 and 12 are printed, the conductor paste amount discharged from the mask M2A is suppressed at the conductor layer edge portions 111 and 121, and the film thickness is thinner than the conductor layer plane portions 110 and 120. Can be formed.
Further, by gradually increasing the weaving density toward the outside, the film thickness of the conductor layer edge portions 111 and 121 can be gradually decreased toward the outside, and the tapered cross-sectional triangle shape can be obtained. it can.

In the above-described embodiment, the method in which the conductor layer edge portions 111 and 121 can be formed in a desired shape in each of the punching process P0 and the printing process P1 has been described, but it is also possible to combine them.
Moreover, in the lamination | stacking crimping | compression-bonding process P3, after drying the conductor layers 11 and 12, the case where lamination | stacking crimping | compression-bonding was taken as an example, you may make it carry out lamination | stacking crimping | bonding in the state where the conductor layers 11 and 12 are undried.
In particular, when the depression 10 is provided in the insulating layer sheet 100 (GS) in the punching process P0, when the conductor layers 11 and 12 are laminated and pressure-bonded in an undried state, the conductor layer 11 conforms to the shape of the depression 10. , 12 are fluidly deformed, so that the conductor layer edge portions 111, 121 can be formed in a desired shape.

Moreover, in the said embodiment, although the method which does not use the intermediate | middle layer 101 which consists of an insulating material as shown in the comparative example 1 was shown in the lamination | stacking crimping | compression-bonding process P3, the shape of the conductor layer edge parts 111 and 121 is shown. In the case where it is formed in advance so as to have a tapered triangular cross section or a gently curved arc-shaped cross section, the intermediate layer 101 is printed by using a paste made of an insulating material in the printing process. Also good.
By using the intermediate layer 101, the shear stress acting on the insulating layer sheet 100 at the time of laminate pressure bonding can be relaxed, the mechanical strength of the element 10 can be improved, and the occurrence of cracks at the time of firing can be suppressed.
In addition to the improvement in detection accuracy, the effect of improving the durability of the element 10 can be expected.

DESCRIPTION OF SYMBOLS 1 Particulate matter detection sensor 10 Particulate matter detection element 100 Insulating layer 11,12 Conductor layer 110,120 Conductor plane part 111,121 Conductor layer edge part 13 Detection part 14 Insulation protective layer 2 Power supply part 3 Measurement part P0 Punching process P1 conductive layer printing step P2 laminating crimping process P3 firing step _{P 111, P 111 A, P} 121, P 121 A edge portion forming the opening ratio _{P 110, P 110 A, P} 120, P 120 A flat portion forming openings Ratio M, MA Opening ratio partial reduction screen

Claims (5)

Laminate in which flat conductor layers ( 11, 11a, 11c, 11d, 11f , 12 , 12a , 12c, 12d, 12f ) and flat insulating layers (100 , 100a , 100c, 100d, 100f ) are alternately stacked. Has a structure,
Using this cross section, a detection unit (13 , 13a , 13c, 13d, 13f ) having the conductor layer as a pair of detection electrodes having different polarities is configured,
A particulate matter detection element for detecting an electrical property that varies depending on the amount of particulate matter deposited on the detection unit and detecting particulate matter in a gas to be measured,
The conductor layer has a constant film thickness and a conductor layer plane portion (110 , 110a , 110c, 110d, 110f , 120 , 120a , 120c, 120d, 120f ) having a strip-shaped cross section,
The conductor layer flat surface portion in at least one of the conductor layers has a shape that protrudes outward in the longitudinal direction at the end portion in the longitudinal direction of the strip shape, and a conductor layer edge portion that serves as an electric field concentration suppressing portion ( 111,111a, 111c, 111d, 111f, 121,121a, 121c, 121d, are provided with a 121f),
The conductor layer edges (111,111a, 111c, 111d, 111f , 121,121a, 121c, 121d, 121f) is particulate matter, wherein polygonal der Rukoto having three or more corners Detection element (10 , 10a, 10c, 10d, 10f ). The conductor layer edge portions (111, 111a, 111c, 111d, 111f, 121, 121a, 121c, 121d, 121f) are more angled outward than corners located on the longitudinal sides of the strip shape. The particulate matter detection element (10, 10a, 10c, 10d , 10f) according to claim 1 , which has at least one small corner portion . In the detection unit (13, 13a, 13f) in which a plurality of the conductor layers (110, 110a, 110f, 120, 120a, 120f) and a plurality of the insulating layers (100, 100a, 100f) are alternately stacked, the plurality of conductive layers, a plurality of the conductive layer edge portions provided on each (111,111a, 111f, 121,121a, 121f ) position of, are aligned in the stacking direction, to claim 1 or 2 The particulate matter detection element described ( 10, 10a, 10f ). In the detection unit (13c, 13d) in which the plurality of conductor layers (110c, 110d, 120c, 120d) and the plurality of insulating layers (100c, 100d) are alternately stacked, the plurality of conductor layers are respectively The particulate matter detection element ( 10c, 10d ) according to claim 1 or 2 , wherein the positions of the plurality of conductor layer edge portions (111c, 111d, 121c, 121d) provided in the substrate are not aligned in the stacking direction. . The particulate matter according to any one of claims 1 to 4, comprising a shielding layer (14) made of an insulating material and covering a whole edge portion of the conductor layer and a part of the flat portion of the conductor layer. Detection element ( 10f ).

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