JP2016099169A - Particulate substance detection sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particulate substance detection sensor capable of improving the detection sensitivity of particulate substance.SOLUTION: A particulate substance detection sensor 1 includes: an accumulation part 10 for accumulating a part of particulate substance contained in an exhaust gas discharged from an internal combustion engine; and at least a pair of detection electrodes 12 disposed on the accumulation part 10. In a direction of alignment of the pair of detection electrodes 12, the width t of the detection electrodes 12 is smaller than a distance S between the pair of detection electrodes 12. With the particulate substance detection sensor 1, the detection sensitivity of the particulate substance can be improved.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particulate matter detection sensor.

  An exhaust gas purification apparatus that collects particulate matter (PM) contained in the exhaust gas is provided in an exhaust pipe of the internal combustion engine. This exhaust gas purification device includes a particulate matter detection device having a particulate matter detection sensor that detects the amount of particulate matter contained in the exhaust gas, and based on information obtained by this particulate matter detection device, Failure detection of the exhaust gas purification device is performed.

  As a particulate matter detection sensor used in an exhaust gas purification apparatus, for example, there is one disclosed in Patent Document 1. The particulate matter detection sensor of Patent Document 1 has a substrate having electrical insulation and a pair of electrodes formed on the surface of the substrate.

JP 59-197847

However, the particulate matter detection sensor disclosed in Patent Document 1 has the following problems.
In the particulate matter detection sensor, improvement in detection sensitivity is desired, and as a means for improving detection sensitivity, it is known to shorten the distance between a pair of electrodes. At this time, the smaller the distance between the pair of electrodes, the better the detection sensitivity of the particulate matter detection sensor. However, the distance between the pair of electrodes is limited by the formation accuracy and forming conditions of the pair of electrodes. Therefore, there is a limit to shortening the distance between the pair of electrodes, and a particulate matter detection sensor that can further improve detection sensitivity is desired.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a particulate matter detection sensor capable of improving the detection sensitivity of particulate matter.

One aspect of the present invention includes a depositing part for depositing a part of particulate matter contained in exhaust gas discharged from an internal combustion engine, and at least a pair of detection electrodes arranged in the depositing part,
The particulate matter detection sensor is characterized in that, in the arrangement direction of the pair of detection electrodes, a width of the detection electrode is equal to or less than a distance between the pair of detection electrodes.

  In the particulate matter detection sensor, when a collection voltage is applied to the pair of detection electrodes of the particulate matter detection sensor, an electric field is formed around the detection electrodes, and the particulate matter is attracted to the detection electrodes. Adhere to. Particulate matter adhering to the surface of one of the pair of detection electrodes moves on the surface of the detection electrode and is deposited on the end facing the other detection electrode.

  If the width of the detection electrode is larger than the distance between the pair of detection electrodes, even if a sufficient amount of particulate matter adheres to form a conduction path on the detection electrode, A conduction path is not formed while moving on the detection electrode. Therefore, it takes time to form a conduction path, and the detection sensitivity is lowered.

  In the particulate matter detection sensor, the width of the detection electrode is equal to or less than the distance between the pair of detection electrodes. For this reason, the distance that the particulate matter attached to the detection electrode moves on the surface of the detection electrode can be shortened. Thereby, the particulate matter adhering to the detection electrode can be quickly moved between the pair of detection electrodes, and a conduction path can be quickly formed by the particulate matter between the pair of detection electrodes. Thereby, the detection sensitivity in the said particulate matter detection sensor can be improved.

  As described above, according to the particulate matter detection sensor, the detection sensitivity of particulate matter can be improved.

FIG. 3 is an explanatory diagram illustrating a particulate matter detection sensor according to the first embodiment. FIG. 3 is an enlarged view of a portion to be deposited of the particulate matter detection sensor in the first embodiment. FIG. 3 is an explanatory diagram illustrating a structure of a particulate matter detection sensor in the first embodiment. FIG. 9 is an explanatory diagram showing a particulate matter detection sensor in Example 2. The enlarged view of the depositing part of the particulate matter detection sensor in Example 2. FIG.

  In the particulate matter detection sensor, the distance between the pair of detection electrodes is preferably 5 μm to 50 μm. In this case, the detection sensitivity of the particulate matter detection sensor can be improved while ensuring the moldability of the pair of detection electrodes.

  Further, the width of the detection electrode is preferably ½ or less of the distance between the pair of detection electrodes. In this case, the detection sensitivity and detection accuracy in the particulate matter detection sensor can be further improved. The width of the detection electrode is more preferably ¼ or less of the distance between the pair of detection electrodes. In this case, the detection sensitivity and detection accuracy in the particulate matter detection sensor can be further improved, and the particulate matter detection sensor with high performance can be obtained.

  The width of the detection electrode is preferably 2.0 μm or more. In this case, the detection sensitivity of the particulate matter detection sensor can be improved while ensuring the moldability of the detection electrode.

  Moreover, it is preferable to have the laminated part which laminated | stacked the said some detection electrode and the several insulating member which has electrical insulation alternately. In this case, the width of the detection electrode and the distance between the pair of detection electrodes can be easily reduced.

Example 1
Examples relating to the particulate matter detection sensor will be described with reference to FIGS.
As shown in FIG. 1, the particulate matter detection sensor 1 includes a depositing part 10 for depositing a part of particulate matter contained in exhaust gas discharged from an internal combustion engine, and at least a pair of parts disposed in the depositing part 10. And a detection electrode 12. In the arrangement direction of the pair of detection electrodes 12, the width t of the detection electrode 12 is not more than the distance S between the pair of detection electrodes 12.

This will be described in more detail below.
The particulate matter detection sensor 1 of this example is for detecting particulate matter contained in exhaust gas discharged from an internal combustion engine mounted on an automobile through an exhaust pipe. Based on the information obtained by the particulate matter detection sensor 1, failure detection of the exhaust gas purification device is performed. The particulate matter detection sensor 1 is disposed so as to protrude to the inside of the exhaust pipe, and the end portion side disposed inside the exhaust pipe in the axial direction of the particulate matter detection sensor 1 is defined as the tip side. The opposite side is the proximal side.

  As shown in FIGS. 1 to 3, the particulate matter detection sensor 1 includes a deposition portion 10 that deposits particulate matter in exhaust gas, and a plurality of detection electrodes 12 that are arranged apart from each other on the deposition portion 10. I have. The particulate matter detection sensor 1 has nine insulating members 13 made of an insulating material, and eight detection electrodes 12 arranged between the insulating members 13. The insulating member 13 and the detection electrodes 12 are connected to each other. Stacked portions 11 that are alternately stacked are formed. The deposited portion 10 is formed at the tip of the particulate matter detection sensor 1 with the end of the detection electrode 12 exposed.

  The insulating member 13 is formed by forming a ceramic material such as alumina, zirconia, magnesia, or beryllia into a flat plate shape. The detection electrode 12 is formed on one surface of the insulating member 13 before sintering by screen printing using a copper paste, a silver paste, or the like. Each insulating member 13 is provided with an electrode lead 14 connected to the detection electrode 12. In the stacked portion 11, the positive electrodes 121 and the negative electrodes 122 are alternately arranged, and the adjacent detection electrodes 12 form a pair of detection electrodes 12. In this example, in the direction in which the pair of detection electrodes 12 are arranged, that is, in the stacking direction of the detection electrode 12 and the insulating member 13, the width t of the detection electrode 12 in the stacked portion 11 is 5 μm. The distance S was set to 20 μm.

  When a collection voltage is applied to the detection electrode 12 in the deposition target portion 10 of the particulate matter detection sensor 1, an electric field is formed around the detection electrode 12, and the particulate matter is attracted to the detection electrode 12. Particulate matter adhering to the detection electrode 12 moves on the surface of the detection electrode 12 and is deposited between the pair of detection electrodes 12. The pair of detection electrodes 12 exposed to the deposition target portion 10 are made conductive by the particulate matter deposited on the deposition target portion 10, and the electrical resistance value between the pair of detection electrodes 12 decreases. As the electrical resistance value between the detection electrodes 12 changes, the amount of current as an electrical signal flowing between the detection electrodes 12 changes. Thereby, the current value output from the particulate matter detection sensor 1 changes. That is, the current value output from the particulate matter detection sensor 1 changes according to the amount of particulate matter deposited in the portion 10 to be deposited, and has information on the amount of particulate matter deposited. By using this current value, it is possible to detect the amount of particulate matter deposited in the portion 10 to be deposited. In this example, the current detected by the particle amount detection means is output to a control unit having a shunt resistance, and the control unit outputs a voltage calculated by the product of the current value and the shunt resistance. This voltage becomes the output of the particulate matter detection sensor 1.

Next, the function and effect of this example will be described.
In the particulate matter detection sensor 1, the width t of the detection electrode 12 is not more than the distance S between the pair of detection electrodes 12. Therefore, the distance S in which the particulate matter attached to the detection electrode 12 moves on the surface of the detection electrode 12 can be shortened. Thereby, the particulate matter adhering to the detection electrode 12 can be quickly moved between the pair of detection electrodes 12, and a conduction path can be quickly formed between the pair of detection electrodes 12 by the particulate matter. Thereby, the detection sensitivity in the particulate matter detection sensor 1 can be improved.

  Further, the width t of the detection electrode 12 is ¼ or less of the distance S between the pair of detection electrodes 12. Therefore, the detection sensitivity and detection accuracy in the particulate matter detection sensor 1 can be further improved, and the high-performance particulate matter detection sensor 1 can be obtained.

  Moreover, it has the laminated part 11 which laminated | stacked the several detection electrode 12 and the several insulating member 13 which has electrical insulation alternately. Therefore, the width t of the detection electrode 12 and the distance S between the pair of detection electrodes 12 can be easily reduced.

  As described above, according to the particulate matter detection sensor 1 of this example, the detection sensitivity of particulate matter can be improved.

(Confirmation test)
In this test, the influence on the detection sensitivity when the width t of the detection electrode 12 in the particulate matter detection sensor 1 was changed was confirmed.
In this test, the particulate matter detection sensor 1 in which the width t of the detection electrode 12 shown in Example 1 is 5 μm and the particulate matter detection sensors 101 to 104 in which the width t of the detection electrode 12 is changed are included. The detection sensitivity was compared. The width t of the detection electrode 12 is 10 μm for the particulate matter detection sensor 101, 15 μm for the particulate matter detection sensor 102, 20 μm for the particulate matter detection sensor 103, and 30 μm for the particulate matter detection sensor 104.

The distance S between the pair of detection electrodes 12 in the particulate matter detection sensors 101 to 104 is 20 μm as in the first embodiment.
Other configurations are the same as those in the first embodiment. Of the reference numerals used in this example or the drawings relating to this example, the same reference numerals as those used in the first embodiment represent the same components as in the first embodiment unless otherwise specified.

The particulate matter detection sensor 1 is disposed so as to protrude from the inner peripheral surface of the exhaust pipe through which the exhaust gas of the internal combustion engine flows toward the center of the exhaust pipe. In the exhaust pipe, exhaust gas having a particulate matter concentration of 3 mg / m ³ was circulated at a flow rate of 20 m / s. The exhaust gas temperature in the vicinity of the particulate matter detection sensor 1 is 200 ° C.

  Under the conditions described above, the detection sensitivity and repeatability of the particulate matter detection sensor 1 were confirmed. The detection sensitivity is determined by the dead mass in the particulate matter detection sensor 1. The dead mass is the amount of particulate matter contained in the exhaust gas flowing through the exhaust pipe until a conduction path is formed in the particulate matter detection sensor 1 and the electrical characteristics of the particulate matter detection sensor 1 change. Is shown. In addition, measurement was performed 5 times and the average value was made into the dead mass.

Table 1 shows the results of the confirmation test. In Table 1, the insensitive mass column shows the measured value of the insensitive mass. Moreover, the column of the judgment 1 shows the judgment with respect to the insensitive mass, “X” (impossible) when the insensitive mass exceeds 30 mg, “O” (good) when the insensitive mass is 30 mg or less and exceeds 20 mg, When the dead mass was 20 mg or less, it was set as “◎” (excellent).
In the column of repeat accuracy, the standard deviation of the dead mass when the dead mass is measured five times is shown. The column of determination 2 indicates determination of repeatability. When the repeatability exceeds 15%, “X” (impossible), and when repeatability is 15% or less and exceeds 10%, “◯” ( Good), and “繰 り 返 し” (excellent) when the repeatability is 10% or less.
Also, the column for comprehensive judgment is “×” when at least one of the dead mass and the repeatability is “×”, both the dead mass and the repeat accuracy are “O” or one of them is “O” and the other is “O”. In the case of “”, “◯” was given, and in the case where both the insensitive mass and the repeatability were “◎”, “◎” was given.

  As shown in Table 1, it was confirmed that when the width t of the detection electrode 12 was 20 μm or less, the dead mass was 30 mg or less, and when the width t of the detection electrode 12 was 5 μm, the dead mass was 20 mg or less. It was. It was also confirmed that when the width t of the detection electrode 12 was 20 μm or less, the repeatability was 15% or less, and when the width t of the detection electrode 12 was 10 μm or less, the repeatability was 10% or less. .

  Therefore, when the width t of the detection electrode 12 is set to be equal to or less than the distance S between the pair of detection electrodes 12, the particulate matter detection sensor 1 with good detection sensitivity and repeatability can be obtained. Further, by setting the width t of the detection electrode 12 to be equal to or less than ½ of the distance S between the pair of detection electrodes 12, the repetition accuracy is further improved, and particles that can stably detect the particulate matter. A particulate matter detection sensor 1 is obtained. Further, by making the width t of the detection electrode 12 equal to or less than ¼ of the distance S between the pair of detection electrodes 12, the detection sensitivity and the repeatability are improved, and the detection sensitivity and stability are excellent. A particulate matter detection sensor 1 is obtained.

(Example 2)
This example shows a particulate matter detection sensor having a structure different from that of Example 1, as shown in FIGS.
The particulate matter detection sensor 100 of this example includes an insulating member 13 in which an insulating material is formed in a substantially rectangular plate shape, and a pair of detection electrodes 12 formed in a flat film shape on the surface of the insulating member 13 by screen printing. have. In the particulate matter detection sensor 100, the surface of the insulating member 13 on which the pair of detection electrodes are formed is a portion to be deposited 10 for depositing particulate matter.

  The pair of detection electrodes 12 includes a positive electrode 125 and a negative electrode 126, and includes an electrode base 123 formed in parallel to the longitudinal direction of the portion 10 to be deposited, and a plurality of electrodes extending from the electrode base 123 perpendicular to the longitudinal direction. Each has a comb tooth portion 124. The positive electrode 125 and the negative electrode 126 are disposed so that the electrode base 123 faces each other, and the comb tooth portion 124 in the negative electrode 126 is disposed between the comb tooth portions 124 in the positive electrode 125.

  In this example, a conduction path is formed by the particulate matter adhered between the comb teeth 124 of the positive electrode 125 and the comb teeth 124 of the negative electrode 126. That is, the direction in which the plurality of comb-tooth portions 124 are arranged is the arrangement direction. In the arrangement direction, the width t of each comb tooth portion 124 was 20 μm, and the distance S between each comb tooth portion 124 was 40 μm.

According to this example, the particulate matter detection sensor 100 having excellent detection sensitivity can be easily manufactured by simplifying the structure.
Also in this example, the same effects as those of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 1,100 Particulate matter detection sensor 10 Deposited part 11 Laminated part 12 Detection electrode 13 Insulating member

Claims (5)

A deposition part (10) for depositing a part of particulate matter contained in exhaust gas discharged from an internal combustion engine, and a pair of detection electrodes (12) arranged in the deposition part (10); ,
In the direction in which the pair of detection electrodes (12) are arranged, the width of the detection electrode (12) is equal to or less than the distance between the pair of detection electrodes (12). , 100).   The particulate matter detection sensor (1, 2) according to claim 1, wherein the width of the detection electrode (12) is ½ or less of the distance between the pair of detection electrodes (12). 100).   The particulate matter detection sensor (1, 100) according to claim 1 or 2, wherein the width of the detection electrode (12) is 2.0 µm or more.   The laminated part (11) which laminated | stacked the said some detection electrode (12) and the several insulating member (13) which has electrical insulation alternately, The one of Claims 1-3 characterized by the above-mentioned. The particulate matter detection sensor (1) according to one item.   The particulate matter detection sensor (1) according to any one of claims 1 to 3, wherein the detection electrode (12) is formed in a flat film shape on the surface of the deposition portion (10). 100).

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