JP5582084B2 - Particulate matter detection sensor and manufacturing method thereof - Google Patents

Description

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

  Collects environmental pollutants contained in combustion exhaust, especially particulate matter (Particulate Matter; hereinafter referred to as PM as appropriate) mainly composed of soot particles and soluble organic components (SOF) in automobile diesel engines, etc. In order to do this, a diesel particulate filter (hereinafter referred to as DPF as appropriate) is installed in the exhaust passage. The DPF is made of porous ceramics having excellent heat resistance, and traps PM by allowing combustion exhaust gas to pass through partition walls having a large number of pores.

  If the amount of collected PM exceeds the allowable amount, DPF may cause clogging and increase the negative pressure or increase the slipping of PM. It is recovering. The regeneration period generally uses the fact that the differential pressure increases with the increase in the amount of PM collected. For this reason, a differential pressure sensor is installed to detect the pressure difference upstream and downstream of the DPF. . In the regeneration process, high-temperature combustion exhaust gas is introduced into the DPF by heater heating or post injection, and PM is combusted and removed.

  On the other hand, sensors capable of directly detecting PM in combustion exhaust are proposed in, for example, Patent Documents 1 and 2. When this sensor is installed downstream of the DPF, the amount of PM passing through the DPF is measured, and an on-board diagnosis (OBD) monitoring of the operating state of the DPF, for example, abnormalities such as cracks and breakage It can be used for detection. Alternatively, it is also considered to install upstream of the DPF, measure the amount of PM flowing into the DPF, and use it to determine the regeneration time instead of the differential pressure sensor.

  Patent Document 1 discloses an electric resistance type smoke sensor in which a pair of comb electrodes are formed on the surface of an insulating substrate, and a heating element is formed on the back surface or inside of the substrate. This sensor makes use of the fact that smoke (fine carbon) has electrical conductivity, and detects a change in electrical resistance value caused by the deposition of smoke between the electrodes serving as the detection unit. As the substrate material, an electrically insulating heat-resistant material is used, and a pair of electrodes is formed by screen-printing on the surface of the flat substrate by pasting a noble metal powder such as Pt or Ag used as an electrode material into a paste. On the back side of the substrate, a heating element is formed in a portion opposite to the electrode, and the detection unit is heated to a desired temperature (for example, 400 ° C. to 600 ° C.) to measure the interelectrode resistance, and then the attached smoke. The detection ability is restored by burning.

Patent Document 2 discloses a sensor element for controlling soot deposition on the sensor.
A basic structure of a conventional PM detection sensor 1z as disclosed in Patent Document 2 is shown in FIG. 13A. A pair of comb-shaped electrodes EL ₁₁ z facing each other with a certain gap provided on an insulating substrate 100z such as alumina ceramics. EL ₁₂ z are formed, and the comb-shaped electrodes EL ₁₁ z and EL ₁₂ z are connected to the power source unit 20 using, for example, a vehicle power source or the like via the lead portions 113 z and 123 z and the terminal portions 114 z and 124 z. ing.
A non-uniform electric field is formed in the space between the interdigitated electrodes EL ₁ 1z and EL ₁₂ z in accordance with the voltage applied from the power supply unit 20 and is contained in the combustion exhaust gas passing through the PM detection sensor 1z. Particles are attracted to and deposited on the comb electrodes EL ₁₁ z and EL ₁₂ z. The amount of soot deposition can be measured by detecting the interelectrode resistance at this time by the detection unit 21.

  Patent Document 3 describes that, in a configuration in which a protective layer is formed on the surface of a comb-shaped measurement electrode, as a manufacturing method, the interval between the measurement electrodes can be reduced by a method using CVD or PVD in addition to screen printing. Yes.

The conventional electric resistance type PM detection sensor 1z has an advantage that a relatively stable output can be obtained with a simple configuration. However, PM is deposited on the insulating substrate 100z, and a pair of comb-shaped electrodes EL ₁₁ z and EL ₁₂ z Until the gap becomes conductive, no change in the electrical resistance value is detected. For this reason, it is a subject to enable detection of PM at an early stage, and in Patent Document 2, control is performed to increase the applied voltage to facilitate attracting soot particles.
However, PM was charged, as shown in FIG. 13 (c), since it is attracted to the stronger detection electrode _EL 11 z, the surface of the _{EL 12} z electric field, easily deposited in the vicinity, exposed between the detection electrode Therefore, it is difficult to deposit on the surface of the insulating substrate 100z, and positively charged PM is attracted to the negative electrode side, and negatively charged PM is attracted to the positive electrode side. For this reason, it is not easy to deposit PM uniformly so as to cause a bias in the PM distribution and cover the entire detection unit.

In addition, failure diagnosis by OBD normally monitors the passage of fine particulate PM of 20 μm or less, and if the interval between the detection electrodes EL ₁₁ z and EL ₁₂ z is smaller, early detection becomes possible. In the conventional screen printing method as described in Documents 1, 2, etc., there are restrictions on the electrode widths and electrode intervals of the comb-shaped electrodes EL ₁₁ z and EL ₁₂ z, and as shown in FIG. The distance between the electrodes is about 30 to 50 μm, and it is difficult to set the distance between the electrodes to 30 μm or less in general screen printing. It was difficult.

Further, as described in Patent Document 3, it is possible to use a thin film forming technique such as PVD method or CVD method, but the electrode interval is still about 20 to 40 μm, and it passes through the DPF. It is not sufficient to detect fine particulate PM. In addition, a dedicated apparatus for forming a thin film is required, which may increase the production cost.
Furthermore, in the conventional method of forming a pair of comb-shaped electrodes on the surface of an insulating substrate by screen printing or the like, the electrode width and the electrode interval are ± 5% depending on fluctuations in shrinkage during firing, printing conditions during electrode formation, and the like. Since individual differences of the degree occur, even if the amount of PM in the gas to be measured is the same, PM is accumulated between the electrodes due to the individual difference of the PM detection sensor, and a change in resistance value is detected. Variations in the amount of change in output with respect to the dead mass until the change and the change in the amount of PM occurred.

  However, in the structure of the PM detection sensor in which a pair of comb-shaped electrodes are formed on the surface of a conventional insulating substrate as described in Patent Documents 1 to 3, etc., the electrode width and electrode interval of the PM detection sensor once completed are corrected. Therefore, it is difficult to reduce such individual differences and further improve detection accuracy.

  Therefore, the present invention improves the detection accuracy in an electrical resistance particulate matter detection sensor used for PM detection in combustion exhaust gas of an internal combustion engine by reducing individual differences in the dimensional accuracy of the width of the detection electrode and the electrode interval. In addition, the distance between the pair of detection electrodes is further reduced so that an abnormality such as slipping of the particulate PM from the DPF can be quickly detected, and further, the particulate matter detection sensor having such a structure is provided. An object of the present invention is to provide a method for manufacturing at a relatively low cost without requiring a complicated production process.

According to the first aspect of the present invention, the combustion exhaust gas of the internal combustion engine is used as a gas to be measured, and is provided in the gas to be measured, and is provided with a flat insulating substrate (100) and a substantially flat membrane-like detection electrode ( EL ₁ , EL ₂ ), and at least a pair of the detection electrodes having different polarities are arranged to face each other in parallel with each other through the insulating substrate, and the insulating property A predetermined voltage is applied between the detection electrode and a particulate matter detection sensor element that uses a cross-section in which the end of the detection electrode is pulled out to at least one side end surface of the insulating substrate as a detection surface while being embedded and held inside the substrate. And an electric power that changes in accordance with the amount of particulate matter deposited on the detection electrode end surface (11, 12) exposed to the detection surface by application of a voltage from the power supply unit. To detect dynamic characteristics A particulate matter detection sensor for detecting the amount of particulate matter in the gas to be measured, with respect to the flat portion of the detection electrode embedded in the insulating substrate. By forming an inclined surface inclined at a predetermined inclined surface forming angle (0 <θ ≦ 45 °) with respect to an orthogonal reference surface, and using the inclined surface as the detection surface, the detection along the detection surface is performed. A particulate matter detection sensor, wherein a distance (T ₁₀ ) between electrodes is adjusted to a predetermined target value (T _10TRG ).

In the invention of claim 2, the distance between the detection electrodes along the detection surface is 2 μm or more and 20 μm or less.

According to a third aspect of the present invention, there is provided a pair of substantially flat film-like detection electrodes opposed via a substantially flat insulating base, and the end of the detection electrode is used as at least one side end face of the insulating base. The amount of particulate matter in the gas to be measured depends on the electrical characteristics that change according to the amount of particulate matter deposited on the surface of the pair of detection electrodes exposed on the detection surface. A method for producing a particulate matter detection sensor for detecting an insulating substrate, wherein at least an insulating substrate forming step of forming a substantially flat insulating substrate using an insulating heat-resistant material, and the surface of the insulating substrate is electrically conductive. A detection electrode forming step of forming a substantially flat membrane-like detection electrode using a conductive material and an insulating substrate on which the detection electrode is formed are stacked, and at least a pair of the detection electrodes face each other with the insulating substrate interposed therebetween Integrated particulate matter detection sensor precursor ( A precursor formation step of forming a _PRE), to form an inclined surface on the end portion of the particulate matter sensor precursor as the cross section of the detection electrode is exposed at a predetermined incline forming an angle (theta), the inclined The surface is the detection surface, and the distance (T ₁₀ ) between the pair of detection electrodes along the detection surface is 1 / the pre-adjustment electrode distance (T _10PRE ) equal to the plate thickness of the insulating substrate (100). and an inter-electrode distance adjusting step of adjusting to a predetermined target value (T _10TRG ) by _setting it to cos θ times.

In the invention according to claim 4, in the inter-electrode distance adjusting step, the thickness of the insulating substrate disposed between the pair of detection electrodes is set to 70% to 100% of the target value, that is, a minus tolerance. setting while, after producing the particulate matter detection sensor precursors, determining the incline forming an angle in accordance with the actual adjustment before the inter-electrode distance (T _10PRE) measurement result.

According to the invention of claim 5, the inclined surface forming angle (θ) is set for each rank by dividing into several groups from the plate thickness distribution of the insulating base.

In the invention of claim 6, when the plate thickness (T _10PRE ) of the insulating substrate, which is the distance between the detection electrodes before adjustment , is equal to or _larger than a predetermined target value, the inclined surface forming angle (θ) is set to 0 °. When the plate thickness of the insulating substrate is thinner than a predetermined target value, the inclined surface forming angle (θ) is set to be larger than 0 ° and not larger than 45 °.

According to the first aspect of the present invention, when the voltage is applied between the detection electrodes from the power supply unit, the detection is performed on the detection surface by the electric field generated between the detection electrodes embedded in the insulating base. Not only the electrode surface but also the surface of the insulating substrate is polarized by dielectric polarization, and the particulate matter contained in the gas to be measured accumulates quickly and uniformly on the detection surface. Can be resolved. Additionally, since the distance between the detection electrodes along said detection plane by adjusting the incline forming angle is adjusted very accurately target the particulate matter in the gas to be measured is deposited above It is possible to stabilize the dead period until electrical characteristics can be detected by the detection unit, and to make the change in output of the detection unit accompanying the accumulation of particulate matter in the gas to be measured constant. Therefore, a particulate matter detection sensor with little individual difference and high reliability can be realized.

According to the second aspect of the present invention, the dead period is eliminated very early, and particulate matter having a particle diameter of 20 μm or less contained in the gas to be measured can be detected.

According to the invention of claim 3, even if the thickness of the insulating substrate varies, it is possible to adjust the inter-electrode distance on the detection surface with extremely high accuracy by forming the inclined surface. A highly reliable particulate matter detection sensor with reduced individual differences can be manufactured.

According to the invention of claim 4, the inter-electrode distance on the detection surface can be adjusted to a value very close to the target value.

Although it is possible to change the set value of the inclined surface forming angle θ for each individual product, there is a possibility that the working efficiency may be lowered. According to the invention of claim 5 , the inclined surface forming angle θ is assigned to each rank. by setting a relatively good efficiency, yet it is possible to adjust the distance between electrodes T ₁₀ to a constant value close to the target value with very high accuracy.

According to the sixth aspect of the present invention, it is possible to arbitrarily adjust in the range of 1.0 to √2 times the original distance between the detection electrodes, which is inevitably generated in the manufacturing process of the PM detection sensor. The variation in the distance between the detection electrodes can be made extremely small and individual differences can be reduced.

The outline | summary of the PM detection sensor in the 1st Embodiment of this invention is shown, (a) is a top view of PM detection sensor before inclined surface formation, (b) is the principal part sectional drawing, (c), The top view which shows PM detection sensor and the whole structure after inclined surface formation, (d) is the principal part sectional drawing. FIG. 1 shows details of a main part of the PM detection sensor of FIG. 1, (a) is an enlarged cross-sectional view of the main part of the PM detection sensor before forming the inclined surface, and (b) is an enlarged main part of the PM detection sensor after forming the inclined surface. Sectional drawing. The schematic diagram which shows the effect of this invention. The effect of this invention is shown with a comparative example, (a) is a characteristic diagram which shows the difference of the change of the output with respect to the to-be-measured gas containing known amount PM in the comparative example 1, the comparative example 2, and Example 1, (b- 1) and (b-2) are characteristic diagrams showing individual differences in Comparative Example 2, and (c-1) and (c-2) are characteristic diagrams showing individual differences in Example 1 of the present invention. FIG. 3 is an exploded perspective view for explaining a method for manufacturing the PM detection sensor according to the first embodiment of the present invention. The outline of the manufacturing method following FIG. 5 is shown, (a-1) is a perspective view of a PM detection sensor precursor before the inclined surface is formed, (a-2) is a cross-sectional view along AA thereof, ( (b-1) is a perspective view of the PM detection sensor after the inclined surface is formed, (b-2) is a cross-sectional view along the line AA, and (c) is an overview of the entire PM detection sensor completed. Diagram. The modification of the PM detection sensor in the 1st Embodiment of this invention is shown, (a) is a development perspective view of PM detection sensor precursor, (b) is sectional drawing of a heat generating body, (c) is PM The perspective view of a detection sensor precursor, (c) is a perspective view of PM detection sensor. PM detection sensor precursor development top view in the 2nd embodiment of the present invention The principal part of PM detection sensor after the inclined surface formation in the 2nd Embodiment of this invention is shown, (a) is a front view, (b) is a side end view, (c) is a bottom view. The PM detection sensor in the 3rd Embodiment of this invention is shown, (a) is a development perspective view of PM detection sensor precursor, (b) is the side end view, (c) is after the inclined surface formation Side view of the PM detection sensor, (d) is a bottom view thereof. The modification of the PM detection sensor in 3rd Embodiment of this invention is shown, (a) is a development perspective view of PM detection sensor precursor, (b) is the side end view, (c) is inclined surface formation The side end elevation of the PM detection sensor after, (d) is the top view. The top view which shows the outline | summary of the PM detection sensor in the 4th Embodiment of this invention. (A) is a block diagram of the conventional PM detection sensor shown as a comparative example, (b) is sectional drawing which shows the detail of a detection part, (c) is sectional drawing which shows the collection state of PM in a comparative example.

A particulate matter detection sensor (hereinafter abbreviated as PM detection sensor) 1 according to the present invention uses a combustion exhaust gas of an internal combustion engine as a gas to be measured, and has a resistance value as an electrical characteristic that varies depending on the amount of PM deposited between detection electrodes. By detecting this, the amount of particulate matter (PM) contained in the gas to be measured is detected.
With reference to FIG. 1 and FIG. 2, the outline | summary of PM detection sensor 1 in the 1st Embodiment of this invention is demonstrated.
As shown in FIGS. 1A and 1B, at least a pair of detection electrodes EL ₁₁ and EL _{12 each} having a constant film thickness of 1 μm or more and 20 μm or less formed of a conductive material such as Pt in a substantially flat film shape is 2 μm. These are arranged in parallel at regular intervals of 20 μm or less and are embedded and held in the substantially flat insulating base 100, and the end surfaces 11 and ₁₂ of these detection electrodes EL ₁₁ and EL ₁₂ are connected to the side end face 10 of the insulating base 100. Particulate matter detection sensor precursor (hereinafter abbreviated as PM detection sensor precursor) 1 drawn to the angle of 0 ° to 45 ° with respect to the reference surface orthogonal to the planar portion of the detection electrodes EL ₁₁ and EL _{12 on} the end face of the _PRE forming an inclined surface having a predetermined inclination angle θ which is inclined in a range of, characterized in that fine adjustment of the detection electrode distance T ₁₀ by the angle of the inclined surface, generated during the production process of the PM detection sensor 1 individual It is intended to improve the detection accuracy by reducing the difference, and to reduce the dead time by efficiently collecting PM with a fine particle size.
In the detection electrodes EL ₁₁ and EL ₁₂ , inclined surfaces can be formed so that the width W of the electrode end surfaces 11 and 12 exposed to the detection surface is constant even if the formation angle θ of the inclined surface changes. Within the range, detection electrode adjustment regions 110 and 120 having a constant electrode width W are formed.

Further, among a plurality of pairs of electrodes EL ₁₁ and EL ₁₂ arranged in parallel, electrodes having the same polarity are connected via the through-hole electrodes 112 and 122 inside the insulating base 100 so that they are in parallel, and are different from each other. Electrode routing portions 111 and 121 that connect the detection electrode adjustment regions 110 and 120 and the through-hole electrodes 112 and 122 while avoiding each other electrode are formed so that the polar electrodes maintain insulation.
Furthermore, as shown in FIG.1 (c), the through-hole electrodes 112 and 122 are connected to the control part 2 provided outside via the detection electrode lead parts 113 and 123 and the electrode terminal parts 114 and 124, respectively. Yes.
The control unit 2 includes a power supply unit 20 and a detection unit 21, and the power supply unit 20 applies a voltage between the detection electrodes EL ₁₁ and EL ₁₂ to facilitate the collection of PM.
For convenience, the detection electrode EL ₁₁ is a positive pole and the detection electrode EL ₁₂ is a negative pole, but it is arbitrary which is positive and negative.
Further, the electrode routing portions 111 and 121 may be formed in any wiring pattern as long as they connect the detection electrode adjustment regions 110 and 120 and the through-hole electrodes 112 and 122 while ensuring insulation.

As shown in FIG. 2 (a), the film thicknesses of the pre-tilt detection electrode end faces 11 _PRE and 12 _PRE exposed on the end face of the PM detection sensor precursor 1 _PRE are the pre-adjustment electrode heights T _11PRE , T _12PRE , When the plate thickness of the insulating base end face 10 _PRE before tilt formation is the pre-adjustment electrode distance T _10PRE , the tilted face is 0 ° or more and 45 ° or less with respect to the reference end face as shown in FIG. Film thicknesses T ₁₁ and T ₁₂ in the direction along the detection surface of the electrode end surfaces 11 and 12 after the inclined surface is formed by cutting, polishing or the like at the formation angle θ, and the detection surface provided on the insulating substrate end surface 10 detecting the inter-electrode distance T ₁₀ along each adjustment before the electrode height _{T 11PRE, T 12PRE, 1 /} cosθ times the unadjusted electrode distance _{T 10PRE,} i.e., inclined surface forming an angle θ of 0 ° or more, 45 ° or less Thus, it can be arbitrarily adjusted in the range of 1.0 to √2.

For example, although the target inter-electrode distance T _10TRG is 10.0 μm, the thickness of the actually formed insulating substrate 100, that is, the pre-adjustment inter-electrode distance T _{10 PRE} is 9.0 μm. In this case, it may be about 1.11 times, the inclined surface forming angle θ is set to about 40.6 °, the inclined surface is formed , and the inclined surface is used as the detecting surface, so that the exposed surface is exposed . it is possible to adjust the distance between electrodes _{T 10} along the detection surface in a very accurately 10.0 [mu] m. Further, as shown in FIG. 5A, the surface of the PM detection sensor precursor 1 _PRE may be uneven on the end surface due to a difference in shrinkage rate or a difference in thermal expansion coefficient. In addition, since PM is collected and deposited on the detection surface, the insulating substrate end surface 10 becomes a three-dimensional obstacle when forming a conductor path between the detection electrode end surfaces 11 and 12. There is no. Further, when the PM detection sensor 1 is in a heating environment such as when the temperature of the gas to be measured is high at the time of PM detection, the detection electrodes EL ₁₁ and EL ₁₂ having a thermal expansion coefficient larger than that of the insulating substrate 100 are expanded. Since the detection electrode end surfaces 11 and 12 protrude outward from the insulating substrate end surface 10, the insulating substrate end surface 10 does not become a three-dimensional obstacle. On the contrary, regardless of the present invention, when the end surface of the insulating base protrudes outward from the end surface of the detection electrode, the detection electrode is moved over the end surface of the insulating base. Since a conductive path is formed between them, the dead period becomes long.

As described above, since the distance between electrodes T ₁₀ is adjusted with extreme precision, the PM is deposited between the electrodes, the resistance value changes varies the dead time to become detected by the detection unit 2 Reduced.
Further, since the cross sections in the thickness direction of the detection electrodes EL ₁₁ , EL ₁₂ and the insulating substrate 100 are exposed as detection surfaces, it is insensitive by reducing the respective film thicknesses (T _11PRE , T _12PRE , T _10PRE ). The period can be reduced.
When the insulating substrate 100 is formed into a sheet by a doctor blade method or the like, the detection electrodes EL ₁₁ and EL ₁₂ are formed into thick films by screen printing, and these are laminated to form the PM detection sensor precursor 1 _PRE , each film Thicknesses (T _11PRE , T _12PRE , T _10PRE ) can be arbitrarily adjusted within a range of 2 μm to 20 μm.

With reference to FIG. 3, the effect of improving the PM trapping property of the PM detection sensor 1 of the present invention will be described. When a voltage is applied from the power source 20 between the detection electrodes EL ₁₁ and EL _12, the detection electrode end surfaces 11 and 12 exposed to the outside of the insulating substrate 100 are polarized, and the oppositely charged PM is detected at the detection electrode end. Collected on the part surfaces 11 and 12.
At this time, an electric field is formed not only on the electrode end surfaces 11 and 12 but also between the detection electrodes EL ₁₁ and EL ₁₂ facing each other inside the insulating substrate 100, so that the dielectric substrate polarizes the insulating substrate end surface 10. In addition, PM is electrically attracted and PM is uniformly deposited between the detection electrode end surfaces 11 and 12, and the dead period is eliminated at an early stage.

With reference to FIG. 4, the precision improvement effect of this invention is demonstrated with a comparative example. This figure (a) shows the change of the output with respect to a known amount of PM, and as a comparative example 1, a PM in which a pair of comb electrodes EL _11z and EL _12Z are formed on the surface of the conventional insulating base 100z shown in FIG. The detection characteristics of the detection sensor 1z are shown. As a comparative example 2, the detection characteristics when the PM precursor 1 _PRE described in the above embodiment is used as it is are shown. The PM detection sensor of the present invention is shown as an example 1. The detection characteristic when 1 is used is shown.
The interelectrode distance of Comparative Example 1 used in this figure is 30 μm, the interelectrode distance of Comparative Example 2 is 9.5 μm, and the interelectrode distance of Example 1 is 10.0 μm.
The dead mass Q _{EMB1 of} Example 1 is the smallest and is about 1/5 of the dead mass Q _REF1 of Comparative Example 1. It can be seen that the PM detection sensor 1 of the present invention can eliminate the dead period at an early stage.
The dead mass Q _REF2 of Comparative Example 2 is _larger than the dead mass Q _{EMB1 of} Example 1. As described above, this is presumably because the detection surface has irregularities and is a three-dimensional obstacle in forming a conductive path.

This figure (b-1) is the result of measuring the individual difference variation of the inter-electrode distance _T10PRE of the PM detection sensor precursor 1 _PRE , and this figure (b-2) does not adjust the inter-electrode distance. The output fluctuation when a known PM amount is detected using a plurality of PM detection sensor precursors 1 _PRE of the present invention is investigated.
As shown in this figure (b-1), in the unadjusted state, the electrode distance T10PRE of the PM detection sensor precursor _1PRE is the measurement level number n = 125, the average is 10.0 μm, and σ0.125. As a whole, the variation was about ± 5%.

The figure (c-1) is are those of the examination of the inter-electrode distance T ₁₀ of the PM detection sensor 1 of the present invention, the view (c-2) is the PM detection sensor of the present invention to adjust the distance between the electrodes The output fluctuation when a known amount of PM is detected using a plurality of 1 is investigated.
In the embodiment of the present invention, when the inter-electrode distance T _10PRE before adjustment is shorter than 10.0 _μm , the detection surface is polished at a uniform inclined surface formation angle θ = 15 °, and 10.0 μm. In the above case, the detection surface was polished with the inclined surface forming angle θ = 0 °.
Electrode distance _{T 10} after the inter-electrode distance adjustment is determined number of levels n = 125, average 10.04Myuemu, improves to Shiguma0.091, as a whole, could be reduced to variation of about ± 3.5% .

Further, an unadjusted inter-electrode distance T _10PRE , that is, the plate thickness of the insulating substrate 100 is set to 70% to 100% of the target value, that is, a minus tolerance, and the PM detection sensor precursor 1 _{PRE is set} to after the preparation, by determining the incline forming an angle θ in accordance with the actual inter electrode distance T _10PRE measurement result, it is possible adjust the distance between electrodes T ₁₀ very close to the target value.
In this case, the set value of the inclined surface formation angle θ can be changed for each individual product, but there is a possibility that the working efficiency may be lowered, and it is ranked into several groups based on the plate thickness distribution of the insulating substrate 100. , by setting the inclined surface forming an angle θ with respect to each rank, a relatively good efficiency, yet it is possible to adjust the value of the inter-electrode distance T ₁₀ constant at very high precision.

For example, when the average value of the plate thickness at the side end portion of the insulating substrate 100 is 9.50 μm, the minimum value is 9.00 μm, the maximum value is 10.00 μm, and σ is 0.125, each PM detection sensor precursor 1 _PRE is A rank when the plate thickness T _10PRE at the end surface of the insulating substrate 100 is _9.7 to 10.0 μm, A rank, 9.3 to 9.7 μm is B rank, 9.0 to 9.4 μm The C rank is A, the A rank has an inclined surface formation angle θ of 17 °, the B rank has an inclined surface formation angle θ of 28 °, and the C rank has an inclined surface formation angle θ of 37 °. mean the thickness _{T 10} at the end surface of the insulating substrate 100 10.03μm, minimum 9.82Myuemu, maximum 10.15Myuemu, it is also possible to adjust to Shiguma0.072.
The figure (b-2), as shown in (c-2), according to the present invention, by reducing the variation of the inter-electrode distance _{T 10,} a variation Delta] Q _EMB1 dead weight be less than Delta] Q _REF2, Moreover, it has been found that the output fluctuation ΔV _{EMB1 with} respect to the known PM amount can also be made smaller than ΔV _REF2 .

With reference to FIGS. 5 and 6, a more specific configuration and manufacturing method of the PM detection sensor 1 according to the first embodiment of the present invention will be described.
Insulating substrate 100 is formed into a predetermined plate thickness (for example, 10 μm as a thickness after firing) by a known method such as a doctor blade method using an insulating heat-resistant material such as alumina, titania or spinel as an insulating substrate forming step. Thus, it is formed into a flat plate shape and punched into a rectangle using a mold or the like. In addition, through holes for forming the through-hole electrodes 112 and 122 are appropriately punched as necessary.
The detection electrodes EL ₁₁ and EL ₁₂ are formed on the surface of the insulating substrate 100 by a known method such as screen printing in a shape corresponding to each electrode pattern using a conductive paste such as platinum as a detection electrode forming step. Print formed.
At this time, as described above, the detection electrode adjustment regions 110 and 120 are formed so that a certain range from the end surface has a certain width, and the detection electrode handling portions 111 and 121 are formed by being connected thereto. ing.
At the same time as the detection electrodes EL ₁₁ and EL ₁₂ are printed, the through-holes 112 and 122 are formed by filling the through-holes of the insulating substrate 100 with the conductor paste.
Detection electrode lead portions 113 and 123 and detection electrode terminal portions 114 and 124 are formed so as to be connected to the detection electrode routing portions 111 and 121 and the through-hole electrodes 112 and 122, respectively.
The detection electrodes EL ₁₁ and EL ₁₂ are stacked so as to alternately face each other with the insulating base 10 interposed therebetween.
Further, in order to form a heating element that generates heat when energized, the heating element 130, the heating element lead portions 131 and 132, and the heating element terminal portion 133 are formed by a known method such as screen printing using a resistance paste and a conductive paste. , 134 are formed by printing.
The heating element 130 is disposed so that the detection surface is at a position thermally lower than the heating element 130.

In the precursor forming step, these are integrally laminated and integrally fired at a predetermined temperature, so that a PM sensor precursor 1 _PRE as shown in FIG. _6A- 1 is formed.
In the present embodiment, the length of the insulating base 100 that is the uppermost layer and the lowermost layer is shortened so that the detection electrode terminal portions 114 and 124 and the heating element terminal portions 133 and 134 are exposed. However, the present invention is not limited to this.
Further, in the present embodiment, the example in which the detection electrodes EL ₁₁ and EL ₁₂ are formed in three layers each is shown, but the number of stacked layers is not limited to this, and can be changed as appropriate.
As shown in FIG. 6 (a-2), a plurality of detection electrodes EL ₁₁ and EL ₁₂ are alternately arranged in parallel via the insulating base 10 and embedded in the insulating base, and the side end face of the insulating base The detection electrode end surfaces 11 _PRE and 12 _PRE are exposed.

Further, the inclined surface forming angle θ is calculated according to the thickness of the insulating substrate 100 of the PM detection sensor precursor 1 _PRE after firing so as to coincide with the target detection electrode distance T10, and the detection electrode distance is calculated. As the adjustment step, the detection surface is formed by a method such as cutting and polishing at a predetermined inclined surface forming angle θ, and as shown in FIGS. (B-1) and (b-2), the detection electrode end portion is formed on the detection surface. surface 11 and 12 will be opposed alternately at a distance _{T 10} between predetermined electrode.

In this way, the power detection unit 20 and the detection unit 21 provided in the control unit 2 are connected to the PM detection sensor 1 thus completed.
The sensor power supply unit 201 applies a voltage between the detection electrodes EL ₁₁ and EL ₁₂ , generates an electric field on the detection surface, and can attract PM in the measurement gas existing around the detection surface by electrostatic force.
The detection unit 21 can measure the resistance value that varies depending on the amount of PM deposited between the detection electrode end surfaces 11 and 12, and can detect the amount of PM contained in the gas to be measured.
The heating element terminal portions 133 and 134 are connected to the heater control unit 202 via heater energization wires 135 and 136 to burn and remove PM deposited between the detection electrode end surfaces 11 and 12 and stabilize the detection resistance. In order to heat to a certain temperature in order to do so, energization is performed as necessary. The PM detection sensor 1 is held by the housing in a state of being covered by a protective cover (not shown), and the detection electrode end surfaces 11 and 12 are placed in the gas flow path to be measured.

With reference to FIG. 7, a PM detection sensor 1a will be described as a modification of the first embodiment of the present invention.
In the above-described embodiment, the example in which the heating element 130 is planarly printed and formed on the surface of the insulating substrate 100 and stacked has been described. However, in this embodiment, the layer on which the detection electrodes EL ₁₁ and EL ₁₂ are formed The heating element 130a is printed and formed on the same layer, and the heating elements 130b and 130c are formed in the through holes that penetrate the insulating substrate 100, and these are laminated, as shown in FIG. The configuration of each of the detection electrodes EL ₁₁ and EL ₁₂ is the same as that of the above embodiment.
Also in the present embodiment, the detection electrode end surfaces 11 and 12 exposed to the detection surface and the insulating base end are formed by forming the inclined surface forming angle θ as shown in FIGS. and adjusting the thickness of the surface 11, the distance between electrodes T ₁₀ can be accurately fixed, the same effect as the above embodiment can be exhibited.

Further, in the present embodiment, the example in which the heating element 130a is formed in each layer is shown, but the formation of the heating element 130a is appropriately thinned according to the amount of generated heat, and is connected via the heating elements 130b and 130c in the through holes. You may make it do.
Furthermore, in the above embodiment, the example in which the detection electrode lead portions 113 and 123 and the detection electrode terminal portions 114 and 124 are formed in the same layer is shown. However, as shown in FIG. Accordingly, the detection electrode lead portion 113, the detection electrode terminal portion 114, the detection electrode lead portion 123, and the detection electrode terminal portion 124 may be formed in different layers. How to arrange the lead part and the terminal part can be selected as appropriate depending on the convenience of wiring to the power supply part 20 and the detection part 21.

A PM detection sensor 1b according to the second embodiment of the present invention will be described with reference to FIGS.
In the above-described embodiment, the configuration in which the end surfaces 11 and ₁₂ of the pair of detection electrodes EL ₁₁ and EL ₁₂ embedded in the insulating substrate 100 are drawn out to the end surface 10 of the insulating substrate 100 has been described. However, the present embodiment is different in that the detection electrode end surface is drawn out in the three directions of the side end surfaces 10 _b1 and 10 _b3 and the bottom surface 10 _b2 of the insulating base 100 formed in a substantially rectangular parallelepiped.
In the present embodiment, as shown in FIG. 8, the detection electrode adjustment regions 110 b 1, 110 b 2, 110 b 3, 120 b 1, 120 b 2, and 120 b 3 are formed so that the width of the portion embedded in the insulating substrate 100 is constant. Therefore, as shown in FIG. 9, when the inclined surfaces are formed in the three directions of the detection surface 1, the detection surface 2, and the detection surface 3, the exposed detection electrode end surfaces 11 _b1 , 11 _b2 , 11 _b3 , 12 _b1 , 12 _b2 , and 12 _b3 are separated from each other by the insulating substrate 100, and the interelectrode distance T ₁₀ is accurately adjusted while keeping the width W of each detection electrode end surface constant. Can do.
In the present embodiment, in addition to the same effects as in the above embodiment, since the detection surface exists in three directions, a degree of freedom is created in the directionality when placed in the measured flow path, and as a PM detection sensor Increased reliability.

With reference to FIG. 10, a PM detection sensor 1c according to a third embodiment of the present invention will be described.
In the above embodiment, the example in which the detection electrodes EL ₁₁ and EL ₁₂ and the detection electrode lead portions 113 and 123 are formed on the surface of one insulating substrate 100 is shown. However, in this embodiment, the insulating substrate 100 The outer periphery is formed in a polygonal shape, and the detection electrode adjustment regions 110c ₁ , 110c ₂ , 110c ₃ , 110c ₄ , 120c ₁ , 120c ₂ , 120c ₃ , 120c ₄ are drawn out so that the ends are exposed toward each side. The detection electrodes EL ₁₁ c and EL ₁₂ c are formed on the electrodes, and these are alternately stacked. Further, the detection electrode lead portions 113 c and 123 c are constituted by through-hole electrodes penetrating the insulating substrate 100, thereby detecting the detection electrode EL. ₁₁ , the electrode ₁₂ is extended in a direction orthogonal to the planar direction of the EL ₁₂ , and the detection electrode terminal portion 114c is formed on the surface of the uppermost layer of the insulating substrate 100. , 124c are different.
Furthermore, the through-hole electrodes 112 and 122 that connect the same polarity of the respective detection electrodes EL ₁₁ and EL ₁₂ , and the through-hole electrodes 112 and 122 that are opposite to the through-hole detection electrodes 121 c and 111 c are opposite to the through-hole electrodes 112 and 122. A gap is provided in order to ensure insulation from the detection electrode handling parts 121c and 111c.

Further, in the present embodiment, the heating element 130c is disposed on the proximal end side with respect to the detection electrodes EL ₁₁ and EL ₁₂ , and the heating element lead portions 131c and 133c penetrate the insulating base 100. It is composed of a through-hole electrode and is extended in a direction perpendicular to the surface on which the heating element 130c is formed.
In addition, in the present embodiment, the inclined surface formation angle θ is formed such that the detection surface of the PM detection sensor 1c tapers toward the tip side.
With such a configuration, as in the above embodiment, the electrode interval T ₁₀ accurately adjusted, in addition to the effect of reducing the variation of the dead weight, detected on each side of the insulating substrate 100 formed in a polygonal shape Since the surface can be formed, the PM detection sensor 1c can be placed without specifying the direction with respect to the flow of the gas to be measured.
Further, in the present embodiment, an example in which the insulating base 100 is formed in a square as a polygon has been shown, but the polygon may have any shape such as a triangle, a pentagon, a hexagon, a dodecagon, and the like. The detection electrodes EL _11c and EL _12c can be formed such that the detection electrode _ends 11c 1 to _n and 12c 1 to _n are exposed toward each side.

In the present embodiment, the detection electrode lead portions 113c and 123c and the heating element lead portions 131c and 132c are filled with an electrode paste in a through hole provided in the insulating substrate 100c, and a plurality of through hole electrodes are formed. Although the laminated example is shown, the detection electrode lead portions 113c and 123c and the heating element lead portions 131c and 132c are constituted by lead wires, and the insulating substrate 100c provided with the through holes is formed into a polygonal column shape extending in the axial direction by extrusion molding. Then, a lead wire may be inserted into the through hole, and the detection electrodes EL ₁₁ c and EL ₁₂ c may be formed at the tip of the insulating substrate 100 c to connect the stacked detection layers.

A modified example 1d of the PM detection sensor according to the third embodiment of the present invention will be described with reference to FIG.
In the PM detection sensor 1c in the third embodiment, the heating element 130c is shown on the base end side of the layer in which the detection electrodes EL _11c and EL _12c are stacked. The difference is that the heating element 130d is disposed on the tip side of the layer in which the detection electrodes EL _11c and EL _12c are stacked.
In the present embodiment, the inclined surface formation angle θ is formed such that the detection surface of the PM detection sensor 1d is tapered toward the base end side.
By adopting such a configuration, the same effects as those of the third embodiment are exhibited. In the present embodiment, the heating element 130d is, the detection electrode EL 11 _d, because it is formed on the distal end side of the layer formed by stacking _EL 12 _d alternately, without waste detected photoelectrically heat generated by the heating element 130d PM accumulated between the extreme surface 11d and 12d can be removed by combustion.

With reference to FIG. 12, a PM detection sensor 1e according to a fourth embodiment of the present invention will be described.
The second, in the third embodiment, the detection electrode end surface _11b 1 to 3 which is exposed to a plurality of detection _{surfaces, 11c 1~4, 11d 1~4, 12b} 1~3, 12c 1~4, 12d1 example to 4 is an internal insulating substrate 100, one sensing electrode handling unit 111b, 111c, 111d, 121b, 121c, connected to 121d, and so as to constitute one detecting electrode _EL 11 d, the _{EL 12} d However, as in this embodiment, the first detection electrodes EL ₁₁ e ₁ , EL ₁₂ e ₁ , the second detection electrodes EL ₁₁ e ₂ , and EL ₁₂ e ₂ are formed separately and independently. You may do it.
Thus, the PM amount deposited between the end surfaces 11e ₁ and 12e _{1 of} the first detection electrodes EL ₁₁ e ₁ and EL ₁₂ e ₁ and the second detection electrodes EL ₁₁ e ₂ and EL ₁₂ e ₂ It is also possible to detect the difference from the PM amount deposited between the end surfaces 11e ₂ and 12e _{2 by} the difference between the outputs V ₁ and V ₂ .

  The PM detection sensor of the present invention formed as described above is applied to an exhaust gas purification device for an internal combustion engine, and is preferably used for detecting discharged particulate matter. Specifically, it 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.

_{DESCRIPTION OF SYMBOLS} 1 PM detection sensor 1 _PRE PM detection sensor precursor 10 Insulating base | substrate inclination end surface 10 Insulating base | substrate end surface 11 and 12 before _PRE inclination formation Detection electrode inclination end surface 11 _PRE , 12 _PRE inclination formation electrode end surface 110, 120 Detection electrode adjustment area | region 111, 120 Detecting electrode routing region 112, 122 Detecting electrode through-hole portion 113, 123 Detecting electrode lead portion 114, 124 Detecting electrode terminal portion 2 Control portion 20 Power supply portion 21 Detecting portion θ Detection surface forming angle
T _10TRG target value T ₁₀ Adjusted electrode distance _{T 10PRE} unadjusted inter-electrode distance (insulating substrate thickness)
Detection electrode height after T ₁₁ , T ₁₂ adjustment T _11PRE , Detection electrode height before T _{12 PRE} adjustment

JP 59-197847 A Japanese translation of PCT publication No. 2008-502892 JP 2009-85959 A

Claims (6)

Combustion exhaust from an internal combustion engine is a gas to be measured, provided in the gas to be measured, a flat insulating base (100), and a substantially flat membrane-shaped detection electrode (EL ₁ , EL ₂ ) made of a conductive material, The at least one pair of the detection electrodes having different polarities are opposed to each other in parallel with each other through the insulating base, and are embedded and held inside the insulating base. A particulate matter detection sensor element that uses, as a detection surface, a cross-section in which an end portion of the detection electrode is drawn to at least one side end surface of the insulating substrate;
A power supply unit (20) for applying a predetermined voltage between the detection electrodes;
A detector (21) for detecting an electrical characteristic that changes according to the amount of particulate matter deposited on the detection electrode end surface (11, 12) exposed to the detection surface by application of a voltage from the power supply unit. And
A particulate matter detection sensor for detecting the amount of particulate matter in a gas to be measured,
An inclined surface is formed which is inclined at a predetermined inclined surface forming angle (0 <θ ≦ 45 °) with respect to a reference plane orthogonal to the plane portion of the detection electrode embedded in the insulating substrate. A particulate matter detection sensor, wherein a distance (T ₁₀ ) between the detection electrodes along the detection surface is adjusted to a predetermined target value (T _10TRG ) by using the detection surface as the detection surface. 2. The particulate matter detection sensor according to claim 1, wherein a distance (T ₁₀ ) between the detection electrodes along the detection surface is 2 μm or more and 20 μm or less. A detection surface having a pair of substantially flat film-like detection electrodes facing each other through a substantially flat insulating base, and the end of the detection electrode being drawn to at least one side end face of the insulating base. And particulate matter detection for detecting the amount of particulate matter in the gas to be measured by electrical characteristics that change in accordance with the amount of particulate matter deposited on the surface of the pair of detection electrodes exposed on the detection surface. A method for manufacturing a sensor, comprising:
at least,
An insulating substrate forming step of forming a substantially flat insulating substrate using an insulating heat-resistant material;
A detection electrode forming step of forming a substantially flat film-like detection electrode on the surface of the insulating substrate using a conductive material;
A precursor forming step of laminating the insulating base on which the detection electrode is formed, and forming at least one pair of the detection electrodes with which the particulate detection substance precursor (1 _PRE ) is opposed with the insulating base interposed therebetween. When,
An inclined surface is formed at an end of the particulate matter sensor precursor at a predetermined inclined surface forming angle (θ) so that a cross section of the detection electrode is exposed , and the inclined surface is used as the detection surface. A predetermined target value is obtained by _setting the distance (T ₁₀ ) between the pair of detection electrodes along the line to be 1 / cos θ times the pre-adjustment electrode distance (T _10PRE ) equal to the plate thickness of the insulating substrate (100). An inter-electrode distance adjusting step of adjusting to (T _10TRG ). In the inter-electrode distance adjusting step, 70% to 100% of the target value the thickness of the disposed the above insulating substrate between the pair of the detection electrodes, i.e., the set tolerances negative eyes, the particulate The manufacturing method of the particulate matter detection sensor according to claim 3, wherein after forming the substance detection sensor precursor, the inclined surface forming angle is determined according to the actual measurement result of the pre-adjustment detection electrode distance ( _T10PRE ). .   The particulate matter detection sensor according to claim 3 or 4, wherein the inclined surface forming angle (θ) is set for each rank by ranking into several groups from the plate thickness distribution of the insulating substrate. Method.   When the plate thickness of the insulating substrate, which is the distance between the detection electrodes before adjustment, is equal to or greater than a predetermined target value, the inclined surface forming angle (θ) is set to 0 °, and the plate thickness of the insulating substrate is set to a predetermined value. 6. The method for manufacturing a particulate matter detection sensor according to claim 3, wherein the inclined surface forming angle (θ) is set to be greater than 0 ° and equal to or less than 45 ° when the value is less than the target value.

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