JP6739363B2 - Particulate matter detection sensor and particulate matter detection device - Google Patents

Description

The present invention relates to a particulate matter detection sensor for detecting the amount of particulate matter contained in exhaust gas, and a particulate matter detection device using the particulate matter detection sensor.

As a particulate matter detection sensor (hereinafter, also referred to as a PM sensor) for detecting the amount of particulate matter (Particulate Matter) contained in exhaust gas, an insulating substrate made of ceramics or the like and a predetermined interval are provided on the insulating substrate. There is known a device including a pair of electrodes arranged to face each other. The particulate matter is made of soot or the like and has electrical conductivity. Therefore, when the particulate matter is deposited between the pair of electrodes, a current flows between the pair of electrodes via the particulate matter. By measuring this current value, the amount of particulate matter contained in the exhaust gas is calculated.

However, in the PM sensor described above, even if a small amount of particulate matter is deposited between the pair of electrodes, a current path due to the particulate matter is not formed between the electrodes, so that no current flows (see FIG. 27). In this PM sensor, a large amount of particulate matter is deposited between a pair of electrodes, and a current path is formed by the particulate matter between the electrodes, and then current begins to flow (see FIG. 28). Therefore, when the particulate matter deposition amount is small, the PM sensor cannot detect the particulate matter because an electric current does not flow between the electrodes. That is, there is a problem that the detection sensitivity of particulate matter is low.

In order to solve this problem, a PM sensor has been invented in which a pair of electrodes is covered with a conductive portion having a higher electrical resistivity than a particulate matter (see Patent Document 1 below). In this PM sensor, when the particulate matter is deposited on the surface of the conductive portion, a current flows from one electrode to the surface of the conductive portion, passes through the particulate material having a lower resistivity, and travels to the other electrode (Fig. 31). Therefore, even if the amount of particulate matter deposited is relatively small, it is considered that the current value between the electrodes changes and that the particulate matter is deposited can be detected.

U.S. Pat. No. 7,543,477

However, the PM sensor of Patent Document 1 has room for improvement in detection accuracy of particulate matter. That is, in the PM sensor, since the electrode is covered by the conductive portion, the particulate matter is deposited on the surface of the conductive portion (see FIG. 31), and when the current flows through the particulate matter, the current Passes through a portion from the electrode to the surface of the conductive portion. Therefore, if manufacturing variations occur in the thickness of this portion, the electrical resistance varies and the current value between the electrodes also varies. Therefore, the amount of particulate matter cannot be accurately measured. Therefore, a PM sensor capable of further improving the detection accuracy of particulate matter is desired.

The present invention has been made in view of the above problems, it is possible to increase the detection sensitivity of the particulate matter, and a particulate matter detection sensor that can improve the detection accuracy, and particles using the particulate matter detection sensor An object of the present invention is to provide a particulate matter detection device.

A first aspect of the present invention is a particulate matter detection sensor (1) for detecting the amount of particulate matter (6) contained in exhaust gas,
A conductive part (made of a conductive material having a higher electrical resistivity than the particulate matter, formed in a plate shape, and having one main surface (S1) as a deposition surface (20) on which the particulate matter is deposited (20). 2) and
A pair of electrodes (3a, 3b) formed on the deposition surface, spaced apart from each other and facing each other;
And a particulate matter detection sensor.

A second aspect of the present invention is a particulate matter detection device (10) comprising a particulate matter detection sensor and a control section (7) electrically connected to the particulate matter detection sensor, wherein the above-mentioned control is performed. The part is a voltage applying part (71) for applying a voltage between the pair of electrodes, a current measuring part (72) for measuring a current flowing between the pair of electrodes, and the exhaust gas based on the measured value of the current. And a calculation unit (73) for calculating the amount of the particulate matter contained in the particulate matter detection device.

The particulate matter detection sensor is made of a conductive material having an electric resistivity higher than that of the particulate matter, and includes a plate-shaped conductive portion. One main surface of this conductive portion is a deposition surface on which particulate matter is deposited. The pair of electrodes is formed on the deposition surface.
Therefore, the detection sensitivity of the particulate matter can be improved. That is, in the particulate matter detection sensor, since a pair of electrodes is formed on the surface of the conductive part (deposited surface), when a voltage is applied between the electrodes in a state where no particulate matter is deposited, The electric current can be applied to the deposition surface instead of the inside of the conductive portion. Therefore, when a small amount of particulate matter is deposited on the deposition surface, an electric current can be passed through the particulate matter having an electric resistance lower than that of the conductive portion, and the current value between the electrodes can be increased. Therefore, even if the deposited amount of the particulate matter is small, it can be detected, and the detection sensitivity of the particulate matter detection sensor can be enhanced.

Further, in the above particulate matter detection sensor, since a pair of electrodes is formed on the main surface of the conductive portion, that is, the deposition surface, a current flows in the deposition surface on the deposition surface (see FIG. 3), Almost no current flows in the thickness direction of the conductive portion. Therefore, the influence of the thickness variation of the conductive portion is less likely to occur, and the detection accuracy of the particulate matter can be improved.

The particulate matter detection device includes the particulate matter detection sensor. Therefore, the detection sensitivity of the particulate matter contained in the exhaust gas can be increased, and the detection accuracy can be improved.

As described above, according to the above aspect, it is possible to increase the detection sensitivity of the particulate matter and improve the detection accuracy, and the particulate matter detection device using the particulate matter detection sensor. Can be provided.

The “main surface” means the surface having the largest area among the surfaces of the conductive portion.
Further, the reference numerals in parentheses described in the claims and the means for solving the problems indicate the correspondence with the specific means described in the embodiments described later, and limit the technical scope of the present invention. Not a thing.

FIG. 3 is a plan view of the particulate matter detection sensor according to the first embodiment and is a view taken in the direction of arrow I in FIG. 2. II-II sectional drawing of FIG. FIG. 3 is an enlarged cross-sectional view of the particulate matter detection sensor in the first embodiment in a state where no particulate matter is deposited. FIG. 3 is an enlarged cross-sectional view of the particulate matter detection sensor according to the first embodiment with a slight amount of particulate matter deposited. The enlarged view of the principal part of FIG. 3 is a graph showing the relationship between the amount of particulate matter deposited and the value of current flowing between electrodes in the first embodiment. FIG. 3 is an exploded perspective view of the particulate matter detection sensor according to the first embodiment. 3 is a conceptual diagram of the particulate matter detection device according to the first embodiment. FIG. FIG. 3 is a diagram showing a mounting position of a particulate matter detection sensor in the first embodiment. FIG. 6 is a sectional view of the particulate matter detection sensor according to the second embodiment. FIG. 13 is a plan view of the particulate matter detection sensor according to the third embodiment, which is a view taken along the line XI of FIG. XII-XII sectional drawing of FIG. 7 is a graph showing the relationship between the amount of particulate matter deposited on the conductive portion and the current flowing between the comb teeth formed on the conductive portion in the third embodiment. 7 is a graph showing the relationship between the amount of particulate matter deposited on the insulating portion and the current flowing between the comb teeth formed on the insulating portion in the third embodiment. The graph which added together FIG. 13 and FIG. 7 is a graph showing the relationship between the surface electrical resistivity ρ and temperature of Sr _{1 -X} La _X TiO ₃ in Embodiment 4. 9 is a graph showing the relationship between the PM injection amount and the sensor output for a plurality of PM sensors having different surface electrical resistivities ρ of the conductive parts in the fourth embodiment. FIG. 6 is a diagram for explaining a method of measuring the surface electrical resistivity ρ in the fourth embodiment. 9 is a graph showing the relationship between sample thickness and electric resistance in Embodiment 4. 6 is a graph showing the relationship between the conductivity and the temperature of SrTiO ₃ in Embodiment 4 investigated by changing the method of measuring the conductivity. FIG. 6 is a diagram for explaining a method for measuring the bulk electrical resistivity in the fourth embodiment. FIG. 3 is an exploded perspective view of a particulate matter detection sensor according to Reference Embodiment 1. FIG. 3 is a perspective view of a particulate matter detection sensor in Reference Embodiment 1. FIG. 24 is a sectional view taken along line XXIV-XXIV of FIG. 23. FIG. 25 is an enlarged view of a main part of FIG. 24. 6 is a conceptual diagram of a particulate matter detection device according to a fifth embodiment. FIG. FIG. 4 is an enlarged cross-sectional view of the particulate matter detection sensor in Comparative Embodiment 1 in a state where a slight amount of particulate matter is deposited. FIG. 6 is an enlarged cross-sectional view of the particulate matter detection sensor in Comparative Example 1 in a state where more particulate matter is deposited. 6 is a graph showing the relationship between the amount of particulate matter deposited and the current in comparative form 1. FIG. 6 is an enlarged cross-sectional view of a particulate matter detection sensor in a comparative form 2 with a slight amount of particulate matter deposited. FIG. 6 is an enlarged cross-sectional view of a particulate matter detection sensor in a state in which a larger amount of particulate matter is deposited in comparative form 2.

The particulate matter detection sensor may be a vehicle-mounted particulate matter detection sensor for mounting on an automobile.

(Embodiment 1)
Embodiments of the particulate matter detection sensor and the particulate matter detection device will be described with reference to FIGS. 1 to 9. The PM sensor 1 of this embodiment is used to detect the amount of the particulate matter 6 (see FIGS. 4 and 5) contained in the exhaust gas. As shown in FIGS. 1 and 7, the PM sensor 1 of this embodiment includes a conductive portion 2 and a pair of electrodes 3 (3a, 3b).

The conductive portion 2 is made of a conductive material having an electric resistivity higher than that of the particulate matter 6, and is formed in a plate shape. As shown in FIG. 2, one main surface S1 of the conductive portion 2 is a deposition surface 20 on which the particulate matter 6 is deposited. The other main surface S2 of the conductive portion 2 is in contact with the substrate portion 4 made of an insulating material.

The pair of electrodes 3 (3a, 3b) is formed on the deposition surface 20. The pair of electrodes 3a and 3b are separated from each other and are arranged to face each other.

The PM sensor 1 of this embodiment is a vehicle-mounted PM sensor to be mounted on a vehicle. As shown in FIG. 9, the vehicle includes an engine 19 and an exhaust pipe 18 connected to the engine 19. The exhaust pipe 18 is provided with a purifying device 17 for removing the particulate matter 6 in the exhaust gas. The PM sensor 1 is attached on the downstream side of the exhaust gas with respect to the purification device 17. In the present embodiment, the PM sensor 1 is used to detect the amount of the particulate matter 6 contained in the exhaust gas that has passed through the purification device 17. Then, using this detected value, a failure diagnosis of the purifying device 17 is performed.
The engine 19 of the present embodiment is a diesel engine equipped with a supercharger, but is not limited to this. The purification device 17 of the present embodiment is an oxidation catalyst (DOC) and a diesel particulate filter (DPF). On the other hand, there is a demand for suppressing the emission of particulate matter also in a gasoline engine, and in order to meet this demand, the PM sensor 1 is provided with a purifying device for a gasoline engine, a so-called three-way catalyst or a particulate filter (GPF). Can also be placed downstream of the. Particularly in a direct-injection gasoline engine, by using the PM sensor 1 of the present embodiment, PM detection accuracy can be improved, so engine feedback control can be suitably performed, and injection control accuracy can be improved. You can

Further, as described above, the PM sensor 1 of this embodiment includes the substrate portion 4 made of an insulating material (ceramics). As shown in FIGS. 2 and 7, a heater 5 is provided in the substrate portion 4. When a large amount of particulate matter 6 is deposited on the deposition surface 20, the heater 5 is used to burn and remove the particulate matter 6.

As shown in FIG. 1, the electrodes 3 a and 3 b include a common portion 30 and a comb tooth portion 31 extending from the common portion 30. Comb-tooth portions 31a formed on one electrode 3a and comb-tooth portions 31b formed on the other electrode 3b are alternately arranged. As shown in FIG. 2, the width W of the comb tooth portions 31 in the arrangement direction (X direction) of the comb tooth portions 31 is shorter than the interval W′ between the comb tooth portions.

The conductive material forming the conductive portion 2 contains a metal oxide having conductivity. As the conductive material, for example, ceramics having a perovskite structure can be used. When the molecular formula of this ceramic is ABO ₃ , it is preferable that A is at least one selected from La, Sr, Ca, and Mg, and B is Ti, Al, Zr, and Y.
The conductive material forming the conductive portion 2 is a material having a higher electrical resistivity than the particulate matter and a slight conductivity.

The electrical resistivity of the particulate matter can be measured by the following powder resistance measuring method. That is, in a state where the powder is put in a predetermined cylindrical container (cross-sectional area A) having a bottom surface and an upper surface as an electrode plate, pressure is applied to the upper electrode plate from above, and the powder (PM) is applied in the vertical axis direction. While compressing, the distance L between the electrodes and the resistance value R between the electrodes are measured. According to this measuring method, the resistivity ρ of the powder (PM) is calculated by R×(A/L).
In this embodiment, the resistance value R was measured using a cylindrical container (cross-sectional area: 2.83×10 ⁻⁵ m ² ) having a cross section of 6 mmφ under a pressure of 60 kgf.
When measured by this method, the resistivity of PM was 10 ⁻³ to 10 ² Ω·cm. This is because the electrical resistivity of generated PM changes depending on the state of the engine. For example, PM discharged from an engine operating under a high load and a high rotation speed has a low unburned hydrocarbon component content and is mostly composed of soot, so that the resistivity is about 10 ⁻³ Ω·cm. is there. Further, since PM discharged from an engine operating at low rotation speed and low load contains a large amount of unburned hydrocarbon components, PM has a high resistivity and is about 10 ² Ω·cm. Therefore, the electric resistivity of the conductive portion 2 in the present embodiment is preferably at least 10 ² Ω·cm or more.

Since the conductive portion 2 has conductivity, a current I flows between the pair of electrodes 3a and 3b even when no particulate matter 6 is deposited on the deposition surface 20, as shown in FIG.

Further, as shown in FIGS. 4 and 5, when the particulate matter 6 is deposited on the deposition surface 20, the current I flows through the particulate matter 6 having a resistivity lower than that of the conductive portion 2. Therefore, as shown in the graph of FIG. 6, as the deposition amount of the particulate matter 6 increases, the current I flowing between the electrodes 3a and 3b increases. Therefore, if this graph is stored in advance, the amount of the particulate matter 6 deposited on the deposition target surface 20 can be calculated. Further, the amount of the particulate matter 6 contained in the exhaust gas can be calculated by using the calculated amount and the time required for depositing the particulate matter 6.

Next, the particulate matter detection device 10 using the PM sensor 1 will be described. As shown in FIG. 8, the particulate matter detection device 10 includes the PM sensor 1 and a control unit 7 connected to the PM sensor 1. The control unit 7 includes a voltage application unit 71, a current measurement unit 72, a calculation unit 73, and a heater control unit 74. The voltage application unit 71 applies a voltage between the pair of electrodes 3a and 3b. Further, the current measuring unit 72 measures the current I flowing between the electrodes 3a and 3b. The heater control unit 74 causes the heater 5 (see FIG. 7) to generate heat and burn the particulate matter 6 when a large amount of the particulate matter 6 is deposited on the deposition target surface 20 and the current I is saturated. The calculation unit 73 uses the measured value of the current I to calculate the amount of the particulate matter 6 deposited on the deposition surface 20. Further, the calculation unit 73 calculates the discharge amount of the particulate matter 6 contained in the exhaust gas per unit time by using the calculated value and the time required for depositing the particulate matter 6.

As shown in FIG. 9, the PM sensor 1 is provided downstream of the exhaust device with respect to the exhaust gas. The PM sensor 1 and the control unit 7 are used to calculate the amount of the particulate matter 6 contained in the exhaust gas that has passed through the purification device 17. The control unit 7 transmits the calculated discharge amount of the particulate matter 6 per unit time to the ECU 16. When the detected amount of the particulate matter 6 exceeds a predetermined value, the ECU 16 determines that the purification device 17 is out of order and notifies the user or the like.

Next, the function and effect of this embodiment will be described. As shown in FIG. 2, the PM sensor 1 of the present embodiment includes a plate-shaped conductive portion 2 made of a conductive material having an electric resistivity higher than that of the particulate matter 6. One main surface S1 of the conductive portion 2 is a deposition surface 20 on which the particulate matter 6 is deposited. A pair of electrodes 3a and 3b are formed on the deposition surface 20.
Therefore, the detection sensitivity of the particulate matter 6 can be improved. That is, in the present embodiment, since the pair of electrodes 3a and 3b are formed on the deposition surface 20 of the conductive portion 2, as shown in FIG. 3, the electrodes 3a and 3b are in a state where no particulate matter 6 is deposited. When a voltage is applied between them, the current I can flow to the deposition surface 20 instead of the inside of the conductive portion 2. Therefore, as shown in FIG. 4, when the particulate matter 6 is slightly deposited on the deposition target surface 20, the current I can be passed through the particulate matter 6 having an electric resistance lower than that of the conductive portion 2, and the electrodes 3a, The current value between 3b can be increased. Therefore, even if the deposition amount of the particulate matter 6 is small, it can be detected, and the detection sensitivity of the particulate matter detection sensor 1 can be enhanced.

Here, as shown in FIG. 27, assuming that the surface of the substrate portion 4 made of an insulating material such as ceramics is a deposition surface 40 and the electrodes 3a and 3b are formed on the deposition surface 40, the particulate matter 6 is generated. The current I does not flow between the electrodes 3a and 3b because a path for the current I is not formed between the electrodes 3a and 3b with only a slight deposition. As shown in FIGS. 28 and 29, when a large amount of the particulate matter 6 is deposited and the path of the current I is formed by the particulate matter 6, the current I starts to flow. Therefore, when the amount of the particulate matter 6 deposited is small, this cannot be detected.

Further, as shown in FIG. 30, it is conceivable to cover the electrodes 3a and 3b with the conductive portion 2, but in this case, when the deposition amount of the particulate matter 6 is small, the current I is mainly applied to the conductive portion 2. Flowing inside. As shown in FIG. 31, in this PM sensor 1, a large amount of particulate matter 6 is deposited on the deposition surface 20, and the electrical resistance via the particulate matter 6 is smaller than the electrical resistance in the conductive portion 2. Then, the electric current I flows through the particulate matter 6. Therefore, when the deposition amount of the particulate matter 6 is small, it cannot be detected.

On the other hand, as shown in FIGS. 3 to 5, if the surface S1 of the conductive portion 2 is used as the deposition surface 20 and the electrodes 3a and 3b are formed on this deposition surface 20, as shown in FIGS. Even when the substance 6 is not deposited at all, the current I can be passed through the deposition surface 20 of the conductive portion 2. Therefore, when the particulate matter 6 is slightly deposited, the current I can be passed through the particulate matter 6 having a resistivity lower than that of the conductive portion 2. Therefore, even if the particulate matter 6 is slightly deposited, the current value between the electrodes 3a and 3b is increased, and it can be detected that the particulate matter 6 is deposited. Therefore, the sensitivity of the PM sensor 1 can be improved.

Further, as shown in FIG. 31, when the electrodes 3a and 3b are covered with the conductive portion 2, the current I is applied to the portion 29 between the electrodes 3a and 3b and the surface S1 (deposited surface 20) of the conductive portion 2. It will flow. Therefore, when manufacturing variation occurs in the thickness of this portion 29, the resistance value between the electrodes 3a and 3b varies and the current value also varies. Therefore, the measurement accuracy of the particulate matter 6 is likely to decrease.
On the other hand, as shown in FIGS. 2 and 3, if the electrodes 3a and 3b are formed on the surface S1 of the conductive portion 2 as in the present embodiment, the current I causes the conductive portion 2 to move in the thickness direction (Z direction). No longer flow to. Therefore, the problem that the electric resistance varies due to the variation in the thickness of the conductive portion 2 does not occur. Therefore, variations in the resistance value of the conductive portion 2 between the pair of electrodes 3a and 3b can be suppressed, and the amount of the particulate matter 6 deposited on the deposition surface 20 can be accurately calculated.

Further, the particulate matter detection device 10 includes the PM sensor 1. Therefore, the detection sensitivity of the particulate matter 6 contained in the exhaust gas can be enhanced, and the detection accuracy of the particulate matter 6 can be enhanced.

Further, as shown in FIGS. 8 and 9, in the present embodiment, the current I flowing between the electrodes 3 a and 3 b of the PM sensor 1 is measured by the control unit 7.
By doing so, the amount of the particulate matter 6 can be measured more accurately. That is, it is possible to measure the current I of the PM sensor 1 by the ECU 16, but in this case, since the distance to the ECU 16 is long, noise may be mixed. On the other hand, when the current I is measured by the control unit 7 arranged near the PM sensor 1, noise is less likely to be mixed. Therefore, the amount of the particulate matter 6 contained in the exhaust gas can be measured more accurately.

Further, as shown in FIG. 1, the electrode 3 of this embodiment includes a common portion 30 and a comb tooth portion 31 extending from the common portion 30. Then, as shown in FIG. 2, the width W of the comb tooth portions 31 in the X direction is made shorter than the interval W′ between the comb tooth portions 31.
Therefore, the width W of the comb tooth portion 31 can be sufficiently shortened. Therefore, it is possible to increase the length in the X direction of the portion between the two comb teeth 31a and 31b adjacent to each other, that is, the portion where the particulate matter 6 can be detected. Therefore, the sticking probability of the particulate matter 6 can be increased, and the detection sensitivity can be further enhanced.

The conductive material forming the conductive portion 2 contains a metal oxide having conductivity.
Metal oxides have high heat resistance. Therefore, the heat resistance of the conductive portion 2 can be improved by using the above conductive material.
Moreover, the use of the above-mentioned conductive material can further improve the measurement accuracy of the particulate matter 6. That is, the electric resistance of the particulate matter 6 greatly changes depending on the temperature. Therefore, when calculating the deposition amount of the particulate matter 6 from the current I flowing between the electrodes 3a and 3b, it is necessary to perform temperature correction. The electrical resistance of the particulate matter 6 decreases as the temperature rises. In addition, the electric resistance of the conductive material containing a metal oxide decreases as the temperature rises. Therefore, when the above conductive material is used as the conductive portion 2, the temperature characteristics of the electrical resistance of the conductive portion 2 and the particulate matter 6 can be made uniform, and the temperature can be easily corrected. Therefore, the measurement accuracy of the particulate matter 6 can be further improved.

Further, as shown in FIG. 2, in the present embodiment, the substrate portion 4 made of an insulating material is arranged on the side of the conductive portion 2 opposite to the side on which the deposition surface 20 is formed. A heater 5 is provided inside the substrate portion 4.
Therefore, the power consumption of the heater 5 can be reduced. That is, it is possible to provide the heater 5 inside the conductive portion 2 without providing the substrate portion 4 (see FIG. 10), but in this case, it is necessary to secure the rigidity of the entire PM sensor 1 by the conductive portion 2 itself. Therefore, it is necessary to make the conductive portion 2 sufficiently thick. In addition, the conductive material forming the conductive portion 2 is selected with priority given to its excellent resistivity and its temperature characteristic, so that a material having excellent thermal conductivity cannot always be used. Therefore, it becomes difficult to heat the deposition surface 20 by the heater 5, and the power consumption of the heater 5 is likely to increase. On the other hand, as shown in FIG. 2, if the substrate portion 4 is provided as in the present embodiment, the rigidity can be secured by the substrate portion 4, so that the thickness of the conductive portion 2 can be reduced. Moreover, since a material having excellent thermal conductivity can be selected as a material forming the substrate portion 4, the deposition surface 20 can be easily heated by the heater 5 in the substrate portion 4. Therefore, the power consumption of the heater 5 can be reduced.

As described above, according to the present embodiment, it is possible to enhance the detection sensitivity of the particulate matter, and to improve the detection accuracy, and the particulate matter detection device using the particulate matter detection sensor. Can be provided.

In the following embodiments, the same reference numerals as those used in the first embodiment among the reference numerals used in the drawings represent the same components and the like as those in the first embodiment unless otherwise specified.

(Embodiment 2)
The present embodiment is an example in which the arrangement position of the heater 5 is changed. As shown in FIG. 10, unlike the first embodiment, the substrate unit 4 is not used in this embodiment. In this embodiment, the heater 5 is provided inside the conductive portion 2. One surface S1 of the conductive portion 2 is the deposition surface 20. A pair of electrodes 3a and 3b are formed on the deposition surface 20.

The function and effect of this embodiment will be described. In this embodiment, since the board portion 4 is not used, the number of parts can be reduced. Therefore, the manufacturing cost of the PM sensor 1 can be reduced. Further, when the conductive portion 2 and the substrate portion 4 are laminated as in the first embodiment, the thermal expansion coefficients of these are different, so when the heater 5 is heated, the PM sensor 1 warps, the conductive portion 2 peels off, and the like. However, since the substrate portion 4 is not used in this embodiment, such a problem is unlikely to occur.
Other than that, it has the same configuration and effects as those of the first embodiment.

(Embodiment 3)
The present embodiment is an example in which the area of the conductive portion 4 is reduced. As shown in FIGS. 11 and 12, in this embodiment, the area of the conductive portion 4 is smaller than that in the first embodiment. The surface S1 of the conductive portion 4 serves as a conductive-side deposition surface 20a on which the particulate matter 6 is deposited.

Further, a plate-shaped insulating portion 8 made of an insulating material is arranged at a position adjacent to the conductive portion 4 in the X direction. A surface S3 of the insulating portion 8 opposite to the side in contact with the substrate portion 4 is used as an insulating-side deposition surface 80 on which the particulate matter 6 is deposited. A pair of electrodes 3a and 3b are formed across the conductive-side deposition surface 20a formed on the conductive portion 2 and the insulating-side deposition surface 80. The area of the conductive-side deposition surface 20a is smaller than the area of the insulating-side deposition surface 80.

The electrodes 3a and 3b include a common portion 30 and a comb tooth portion 31 extending from the common portion 30, as in the first embodiment. The number of comb tooth portions 31 formed on the conductive-side deposited surface 20 a is smaller than the number of comb tooth portions 31 formed on the insulating-side deposited surface 80.

Since the conductive portion 2 is made of a conductive material as in the first embodiment, even if the particulate matter 6 is slightly deposited on the conductive-side deposition surface 20a, the comb tooth portion 31a formed on the conductive-side deposition surface 20a is formed. , 31b flows a current I ₁ . Therefore, the relationship between the amount of the particulate matter 6 deposited on the conductive-side deposition surface 20a and the current I ₁ is as shown in the graph of FIG.

Further, since the insulating portion 8 is made of an insulating material, the current I ₂ does not flow even if only a small amount of the particulate matter 6 is deposited on the insulating-side deposition surface 80, but a normal electrical resistance sensor that does not use a conductor is used. Similarly to the above, an electrostatic force is generated between the electrodes, which has the function of arranging the particulate matter 6 along the electrostatic field. When a conductive path formed by arranging the particulate matter 6 between the comb tooth portions 31a and 31b on the insulating-side deposition surface 80 is formed by the action of the electrostatic force, the current I ₂ flows between them. Therefore, the relationship between the amount of the particulate matter 6 deposited on the insulating-side deposition surface 80 and the current I ₂ is as shown in the graph of FIG. The conductive path formed between the comb teeth 31a and 31b of the insulating-side deposited surface 80 is formed of only the particulate matter 6 and has a low resistance. Therefore, the current flowing between the comb teeth 31a and 31b is low. There is a large amount. Therefore, the slope of the graph is steeper than that of FIG.

The relationship between the amount of the particulate matter 6 deposited on the two deposition surfaces 20a and 80 and the current I (=I ₁ +I ₂ ) flowing between the pair of electrodes 3a and 3b is as shown in the graph of FIG. .. This graph is a combination of the graphs of FIGS. 13 and 14. As shown in FIG. 15, the slope of the current I is small until the comb teeth 31a and 31b formed on the insulating-side deposition surface 80 are connected by the particulate matter 6, and then the slope of the current I is large. Further, in the present embodiment, when a large amount of particulate matter 6 is deposited and the current I flowing between the electrodes 3a and 3b exceeds a predetermined threshold value I _th , the heater 5 is caused to generate heat and the particulate matter 6 is removed. I'm trying to burn. The current I reaches the threshold value I _th after the slope becomes large.

The function and effect of this embodiment will be described. The PM sensor 1 of the present embodiment includes a conductive portion 2 and an insulating portion 8, and a pair of electrodes 3a and 3b are formed across the conductive portion 2 and the insulating portion 8. Therefore, even if the particulate matter 6 is slightly deposited on the conductive portion 2, the current I flows between the electrodes 3a and 3b, and the deposition amount of the particulate matter 6 can be detected. Further, in the particulate matter detection device 10 of the present embodiment, when a large amount of particulate matter 6 is deposited on the PM sensor 1 and the current I becomes steep and exceeds the threshold value I _th , the particulate matter 6 is _generated. Is configured to perform combustion. Therefore, it is possible to reduce the variation σ _PM of the particulate matter 6 when the current I reaches the threshold value I _th . Therefore, it becomes easy to burn the particulate matter 6 at an appropriate timing.
Other than that, it has the same configuration and effects as those of the first embodiment.

(Embodiment 4)
The present embodiment is an example in which the conductive material forming the conductive portion 2 is changed. In this embodiment, the surface electrical resistivity ρ of the conductive material is measured as follows. That is, first, the sample 25 shown in FIG. 18 is prepared. This sample 25 is made of a conductive material and has a thickness T of 1.4 mm, and a pair of measurement electrodes 39 formed on the main surface of the plate substrate 251 and having a length L and an interval D. Have and. Such a sample 25 is formed, and the electrical resistance R (Ω) between the pair of measurement electrodes 39 is measured. The surface electrical resistivity ρ is calculated by the following equation (1).
ρ=R×L×T/D (1)

In addition, in the present specification, when simply described as “electrical resistivity”, it means so-called bulk electrical resistivity. For example, as shown in FIG. 21, a bulk sample 259 including a substrate part 250 made of a conductive material and a pair of measurement electrodes 391 formed on the side surfaces of the substrate part 250 is prepared. It can be calculated by measuring the electric resistance between 391. In addition, when described as “surface electrical resistivity ρ”, the sample 25 shown in FIG. 18 was prepared, the electrical resistance R between the measurement electrodes 39 was measured, and the value calculated using the above formula (1) was calculated. means.

Further, in this embodiment, as shown in FIG. 16, a conductive material having a surface electrical resistivity ρ of 1.0×10 ^{7 to} 1.0×10 ¹⁰ Ω·cm is used in the temperature range of 100 to 500° C. Thus, the conductive portion 2 is formed.

As a conductive material having a surface electric resistivity ρ satisfying the above numerical range, a ceramic having a perovskite structure represented by a molecular formula of ABO ₃ can be used. For example, at least one selected from La, Sr, Ca, and Mg can be used as A in the molecular formula, and at least one selected from Ti, Al, Zr, and Y can be used as B.

In the present embodiment, the main component of A in the above formula is Sr and the sub-component is La. Further, B in the above molecular formula is Ti. FIG. 16 shows the relationship between the surface electrical resistivity ρ of this ceramic (Sr _1-X La _X TiO ₃ ) and the temperature. As shown in the figure, when X is set to 0.016 to 0.036, the surface electrical resistivity ρ of Sr _1-X La _X TiO ₃ is 1.0×10 ⁷ in the temperature range of 100 to 500° C. It becomes about 1.0×10 ¹⁰ Ω·cm. Therefore, this ceramic can be preferably used as a material for forming the conductive portion 2.

Moreover, as shown in FIG. 16, when La is not added (SrTiO ₃ ), the surface electrical resistivity ρ is about 1.0×10 ^{5 to} 1.0×10 ¹¹ Ω in the temperature range of 100 to 500° C.・It becomes cm. From this, it can be seen that the inclusion of La in the above ceramics causes less change in the surface electrical resistivity ρ with temperature.

In obtaining the graph of FIG. 16, the surface electrical resistivity ρ was measured in more detail as follows. That is, ceramics in which _X in Sr _1-X La _X TiO ₃ was set to 0, 0.016, 0.02, and 0.36 were prepared, and sample 25 (FIG. 18) was prepared using these ceramics. Each sample 25 includes a plate-shaped substrate 251 having a thickness T of 1.4 mm, and a pair of measurement electrodes 39 formed on the main surface of the plate-shaped substrate 251 and having a length L of 16 mm and an interval D of 800 μm. Prepare Then, this sample 25 was heated to 100 to 500° C. in the atmosphere, a voltage of 5 to 1000 V was applied between the measurement electrodes 39, and the electric resistance R was measured. Then, the surface electrical resistivity ρ was calculated using the above formula (1).

FIG. 17 shows a graph in which the relationship between the amount of PM injected to the PM sensor 1 and the sensor output of the PM sensor 1 is investigated by changing the surface electrical resistivity ρ of the conductive portion 2. This graph was obtained as follows. First, the conductive portion 2 is formed by using a conductive material having a surface electrical resistivity ρ of 2.3×10 ⁶ , 1.0×10 ⁷ , 1.0×10 ¹⁰ and 3.2×10 ¹⁰ Ω·cm, respectively. Was formed, and the PM sensor 1 including each conductive portion 2 was created. Then, the exhaust gas having a PM content of 0.01 mg/l was injected to each PM sensor 1, and a part of the injected PM was deposited on the deposition surface 20 of the PM sensor. Further, the current I flowing between the pair of electrodes 3a and 3b was converted into a voltage by using a shunt resistance, and a sensor output was obtained. The distance between the electrodes 3a and 3b was 80 μm, the applied voltage was 35 V, and the measurement temperature was 200° C. FIG. 17 is a graph showing the relationship between the PM injection amount and the sensor output.

As shown in the figure, when the surface electrical resistivity ρ of the conductive portion 2 is 1.0×10 ^{7 to} 1.0×10 ¹⁰ Ω·cm, PM is slightly ejected and the PM sensor 1 The sensor output increases. That is, it can be seen that the PM sensor 1 has high sensitivity. Further, as PM adheres, the sensor output changes greatly. Therefore, it can be seen that if the surface electrical resistivity ρ of the conductive portion 2 is within the above range, the PM sensor 1 has high sensitivity and the amount of accumulated PM can be accurately measured.

On the other hand, when the surface electric resistivity ρ is out of the above range, such an effect cannot be sufficiently obtained. For example, when the surface electrical resistivity ρ is 3.2×10 ¹⁰ Ω·cm, the sensor output hardly increases when the PM deposition amount is small. That is, there is a dead period. This is because the surface electric resistivity ρ of the conductive portion 2 is too high, and the current I is difficult to flow between the electrodes 3a and 3b. Therefore, a large amount of PM is deposited and a current path due to PM is formed, and then the current I It is thought that this is because the flow starts.

When the surface electrical resistivity ρ is, for example, 2.3×10 ⁶ Ω·cm, the sensor output hardly changes even if the PM deposition amount changes. It is considered that this is because the surface electrical resistivity ρ is too low, so that even if PM is deposited, the current I does not flow into the PM so much that the current value between the electrodes 3a and 3b does not easily change. Therefore, in this case, it is found that it is difficult to accurately measure the PM deposition amount using the sensor output.

Next, the depth from the surface of the current I flowing in the sample 25 (see FIG. 18) will be described with reference to FIG. The graph of FIG. 19 was created as follows. First, a conductive material was formed into a sheet shape, the measurement electrode 39 was printed on the surface thereof, and baked to prepare a sample 25. The thickness T of the sample 25 was set to 10 μm, 20 μm, 40 μm, 45 μm, 50 μm, 80 μm, 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 1.4 mm, 2.0 mm. These samples 25 were heated to 200° C. to remove the influence of moisture, and a voltage of 500 V was applied between the pair of measurement electrodes 39 to measure the electric resistance R. The length L of the measurement electrode 39 was 16 mm, and the distance D was 800 μm. Then, the electric resistance when the thickness of the sample 25 was 10 μm was used as a reference (that is, 100%), and the relationship between the ratio of the electric resistance R of each sample 25 and the thickness was plotted.

As shown in FIG. 19, when the thickness of the sample 25 is in the range of 10 μm to 0.1 mm, the electric resistance decreases as the thickness increases, but when it exceeds 0.1 mm, it hardly changes. From this, it can be seen that the current I flows only from the surface of the sample 25 to a depth of 0.1 mm. In this embodiment, when measuring the surface electrical resistivity ρ, the thickness T of the sample 25 is set to 1.4 mm. Therefore, a sufficient thickness for passing the current I can be secured.

Next, with reference to FIG. 20, the relationship between the electrical resistivity and the surface electrical resistivity ρ of SrTiO ₃ and the temperature will be described. The graph of FIG. 20 was created as follows. That is, sample 25 (see FIG. 18) was prepared using SrTiO ₃ , and the surface electrical resistivity ρ was measured while changing the temperature. Further, a bulk sample 259 (see FIG. 21) was prepared using SrTiO ₃ , and the bulk electrical resistivity was measured while changing the temperature. The graph of FIG. 20 shows the relationship between the measured electric resistivity and surface electric resistivity ρ and the temperature. It can be seen from the figure that the bulk electrical resistivity and the surface electrical resistivity ρ have completely different values.

Next, the function and effect of this embodiment will be described. In this embodiment, the conductive portion 2 is formed by using a conductive material having a surface electrical resistivity ρ of 1.0×10 ^{7 to} 1.0×10 ¹⁰ Ω·cm in the temperature range of 100 to 500° C. is there.
Therefore, as shown in FIG. 17, it is possible to obtain the PM sensor 1 which has a small dead period and whose sensor output largely changes due to the adhesion of the particulate matter.

Further, in this embodiment, the numerical range of the surface electrical resistivity ρ is specified. Therefore, it is easy to optimize the electric characteristics of the conductive portion 2. That is, in the PM sensor 1 of the present embodiment, the electrodes 3a and 3b are formed on the main surface S1 (see FIG. 2) of the conductive portion 2, so that when the PM sensor 1 is used, the current I is equal to that of the conductive portion 2. It flows near the surface. Therefore, it can be said that the surface electrical resistivity ρ measured by passing the current I near the surface of the plate-shaped substrate 251 (see FIG. 18) is an electrical characteristic measured in a state close to the actual usage state of the PM sensor 1. Therefore, by defining the numerical range of the surface electrical resistivity ρ, it is possible to define the electrical characteristics of the conductive portion 2 in a state close to the actual use state.

Further, in this embodiment, as the conductive material forming the conductive portion 2, ceramics having a perovskite structure is used. When the molecular formula of this ceramic is ABO ₃ , it is preferable that A is at least one selected from La, Sr, Ca, and Mg, and B is at least one selected from Ti, Al, Zr, and Y.
Such ceramics have high heat resistance and are unlikely to chemically react with substances contained in exhaust gas. Therefore, it can be suitably used as a conductive material for the PM sensor 1 exposed to exhaust gas.

It is particularly preferable that A in the above molecular formula is Sr as a main component, La is a sub-component, and B is Ti.
As shown in FIG. 16, such a ceramic has a small change in the surface electrical resistivity ρ even if the temperature changes. It is considered that this is an effect due to the addition of La. If the conductive portion 2 is formed using such ceramics, it becomes possible to use an inexpensive measuring circuit for measuring the output of the PM sensor 1. That is, as shown in FIG. 16, in the ceramic containing no La (SrTiO ₃ ), the surface electrical resistivity ρ changes greatly to about 1×10 ⁵ to 1×10 ¹¹ Ω·cm in the temperature range of 100 to 500° C. To do. Therefore, the conductive portion 2 formed by using this ceramic (SrTiO ₃ ) flows only a small current near 100° C. and a large current near 500° C. Therefore, it is necessary to use an expensive measuring circuit having a wide current measuring range. On the other hand, if the ceramic containing La (Sr _1-X La _X TiO ₃ ) is used, the change in the surface electrical resistivity ρ in the temperature range of 100 to 500° C. can be reduced. Therefore, it is possible to reduce a change in the current flowing through the conductive portion 2 in this temperature range, and it is possible to use an inexpensive measurement circuit having a narrow current measurement range.
Other than that, it has the same configuration and effects as those of the first embodiment.

(Reference form 1)
The present embodiment relates to a PM sensor 1 capable of enhancing detection sensitivity while providing a conductive portion so as to cover the pair of electrodes 3a and 3b.
In the first embodiment, the electrode 3 is provided on the surface of the conductive portion 2. As a result, a current is applied to the surface of the conductive portion 2, that is, the deposition surface 20. According to this structure, even if a small amount of PM is deposited on the deposition surface 20, the current value changes, so that the PM detection sensitivity can be increased.
On the other hand, in the present embodiment, the detection sensitivity of PM is enhanced by defining the relative relationship between the thickness of the conductive portion 2 and the thickness of the electrode 3.

Main parts of the present embodiment will be described with reference to FIGS.
The particulate matter detection device 10 of the present embodiment includes the PM sensor 101 and the control unit 7 connected to the PM sensor 101, as in the first embodiment. The control unit 7 has the same configuration as that of the first embodiment, and thus the description thereof is omitted.
The PM sensor 101 of the present embodiment example includes a substrate portion 401 made of an insulating material and a plurality of electrode plate portions 402 having electrodes formed thereon.
The board portion 401 is made of the same material as the board portion 4 of the first embodiment. Further, the electrode plate portion 402 is a plate-shaped electrode substrate portion 412 made of an insulating material, the detection electrode portions 301 and 302 formed on the electrode substrate portion 412, and an extension electrically connected to the detection electrode portions 301 and 302. And a projecting portion 303. As will be described later, the detection electrode portions 301 and 302 are covered with the conductive portion 200 (see FIG. 24).
The substrate part 401 and the electrode plate part 402 are formed in a rectangular plate shape. Further, the extending portion 303 is formed on the electrode substrate portion 412 so as to extend in the longitudinal direction. One end of the extension part 303 is electrically connected to the control part 7, and the other end is connected to the detection electrode parts 301 and 302.

As shown in FIG. 22, the detection electrode portions 301 that are positive electrodes and the detection electrode portions 302 that are negative electrodes are alternately arranged. In this way, the plurality of electrode plate portions 402 are laminated so that adjacent electrodes have different polarities. The substrate portion 401 is arranged on one side of the electrode plate portion 402 in the stacking direction, and the heater plate portion 403 having the heater 5 is arranged on the other side. The substrate portion 401 and the heater plate portion 403 sandwich a plurality of electrode plate portions 402 from the stacking direction. This constitutes a laminated body.

As shown in FIG. 23, the detection electrode portions 301 and 302 and the electrode substrate portion 412 are exposed from a part of the side surface 111 of the PM sensor 101. The exposed detection electrode portions 301 and 302 and the electrode substrate portion 412 are covered with a conductive portion 200 having a predetermined thickness, as shown in FIG. The conductive portion 200 can be formed of the same material as that of the first embodiment.
The particulate matter is deposited on the deposition surface 201 of the conductive portion 200. The deposition surface 201 is formed on the side of the conductive portion 200 opposite to the side on which the detection electrode portions 301 and 302 are arranged. Since the electrical resistivity of the conductive portion 200 is higher than the electrical resistivity of the particulate matter, a current is more likely to flow in the particulate matter than the conductive portion 200. Therefore, similar to the first embodiment, when the particulate matter is deposited on the deposition target surface 201, the electrical resistance between the detection electrode portions 301 and 302 is lower than when the particulate matter is not deposited. Therefore, the current measurement value by the current measurement unit 72 of the control unit 7 (see FIG. 8) becomes large. The calculation unit 73 uses this measured value to calculate the deposition amount of the particulate matter.

Note that, as shown in FIG. 24, the thickness Ws of the conductive portion 200 is formed to be smaller than the thickness We of the detection electrode portions 301 and 302.

As described above, by making the thickness Ws of the conductive portion 200 smaller than the thickness We of the detection electrode portions 301 and 302, the detection sensitivity of the particulate matter can be improved.

The function and effect of this embodiment will be described in detail.
As shown in FIGS. 22 and 24, an electrode substrate portion 412 made of an insulator is interposed between the pair of detection electrode portions 301 and 302. Therefore, even if a voltage is applied to the pair of detection electrode portions 301 and 302, no current flows in the electrode substrate portion 412. However, since a part of the pair of electrodes 301 and 302 is covered with the conductive portion 200, a current flows through the conductive portion 200.
As shown in FIG. 25, the current flowing from one detection electrode portion 301 of the pair of detection electrode portions 301 and 302 bends in the conductive portion 200 and reaches the other detection electrode portion 302. Therefore, even if the particulate matter is not attached to the deposition target surface 201, a part of the current can flow to the deposition target surface 201. At this time, if the thickness Ws of the conductive portion is thicker than the thickness We of the detection electrode portion, the distance until the current reaches the deposition target surface 201 becomes long, so that the ratio of the current flowing in the conductive portion 200 is high. Therefore, the amount of current flowing through the deposition surface 201 is reduced. Therefore, it becomes difficult to sufficiently enhance the PM detection sensitivity.
However, if the thickness Ws of the conductive portion 200 is smaller than the thickness We of the detection electrode portion as in the present embodiment, the amount of current flowing in the conductive portion 200 can be reduced, and the deposition surface 201 can be reduced. A large amount of current can be applied to it. Therefore, when the particulate matter adheres to the deposition surface 201, an electric current easily flows through the particulate matter.

Therefore, even if the particulate matter is slightly deposited on the conductive portion 200, the rate of change of the current value becomes large, and the detection sensitivity of the particulate matter can be improved.

(Embodiment 5)
As shown in FIG. 26, the particulate matter detection device 102 of the present embodiment includes a temperature measurement unit 501 that detects the temperature of exhaust gas. In addition to the configuration of the first embodiment, the control unit 701 includes a resistance value correction unit 75 that corrects the resistance value of the conductive unit 20 according to the temperature of exhaust gas. That is, the control unit 701 of the present embodiment includes a voltage application unit 71 that applies a voltage to the pair of electrodes, a current measurement unit 72 that detects the value of the current flowing between the pair of electrodes, and a heater control unit that controls the heater 5. 74, a calculation unit 73 that calculates the deposition amount of the particulate matter from the measurement value detected by the current measurement unit, and calculates the discharge amount of the particulate matter contained in the exhaust gas per unit time, and the resistance value correction And a section 75.

As the temperature measuring unit 501, a known temperature sensor for exhaust gas can be used, and for example, a temperature sensor using a thermistor as a heat sensitive element can be adopted. The temperature measuring unit 501 is provided in the vicinity of the PM sensor 1 attached to the exhaust pipe, and transmits information on the detected temperature to the resistance value correcting unit 75 of the control unit 701. By providing the temperature measuring unit 501 near the PM sensor 1, it becomes possible to use the measured value of the temperature near the PM sensor 1 for the correction of the resistance value of the conductive unit 2. Therefore, the accuracy of the resistance value correction can be improved.
Although not shown, information on the temperature measured by the temperature measuring unit 501 is also sent to the ECU 16 and used for engine injection control and the like.

In the present embodiment, the calculation unit 73 time-differentiates the measurement value obtained by the current measurement unit 72 to calculate a time differential value. This time differential value correlates with the number of particulate matter in the exhaust gas. Further, the calculation unit 73 has quantity correction data for correcting the number of particulate matter in the exhaust gas per unit volume. The calculation unit 73 can calculate the quantity of the particulate matter per unit volume in the exhaust gas by using the time differential value and the quantity correction data.

The resistance correction unit 75 stores data (temperature characteristic data) regarding the relationship between the temperature of the conductive unit 2 and the electric resistance. The resistance correction unit 75 calculates the corrected resistance value of the conductive unit 2 using the temperature detected by the temperature measurement unit 501 and the temperature characteristic data. Then, the correction resistance value is used to perform correction for reducing the influence of the change in the electric resistance of the conductive portion 2 included in the electric resistance between the electrodes 3a and 3b due to the temperature.

This makes it possible to reduce the influence of the exhaust gas temperature on the conductive portion 2 when detecting the amount of particulate matter. Therefore, the detection accuracy of the particulate matter can be improved.

(Other embodiments)
Although the respective embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be applied to various embodiments without departing from the scope of the invention, and particularly in combination. It is also possible to combine the embodiments with each other as long as they do not cause any problems.

For example, the control unit 701 of the particulate matter detection device 102 described in the fifth embodiment is premised on the configuration of the PM sensor 1 of the first embodiment, but the PM sensors of the second to fourth embodiments may be adopted.
Further, in the reference embodiment 1, the conductive portion 200 is provided on the side surface 111 of the PM sensor, but it may be provided on the end surface.

1 Particulate Matter Detection Sensor 10 Particulate Matter Detector 2 Conductive Part 20 Deposited Surfaces 3a, 3b Electrode 6 Particulate Matter 7 Control Part

Claims (9)

A particulate matter detection sensor (1) for detecting the amount of particulate matter (6) contained in exhaust gas, comprising:
A conductive part (made of a conductive material having a higher electrical resistivity than the particulate matter, formed in a plate shape, and having one main surface (S1) as a deposition surface (20) on which the particulate matter is deposited (20). 2) and
A pair of electrodes (3a, 3b) formed on the deposition surface, spaced apart from each other and facing each other;
And a particulate matter detection sensor. The electrode includes a common portion (30) and a comb tooth portion (31) extending from the common portion, and the comb tooth portion (3a) formed on one of the pair of electrodes (3a). 31a) and the comb tooth portion (31b) formed on the other electrode (3b) are arranged alternately, and the width (W) of the comb tooth portion in the arrangement direction of the comb tooth portion is The particulate matter detection sensor according to claim 1, wherein the distance between the comb tooth portions (W') is made shorter. The particulate matter detection sensor according to claim 1 or 2, wherein the conductive material forming the conductive portion contains a metal oxide having conductivity. A substrate portion (4) made of an insulating material is disposed on the side of the conductive portion opposite to the side on which the deposition surface is formed, and the particulate matter deposited on the deposition surface is disposed in the substrate portion. The particulate matter detection sensor according to claim 1, further comprising a heater (5) for burning the. The particulate matter detection sensor according to any one of claims 1 to 3, wherein a heater that burns the particulate matter deposited on the deposition surface is provided in the conductive portion. A plate-like substrate (251) made of the above conductive material and having a thickness T of 1.4 mm, and a pair of measuring electrodes (39) formed on the main surface of the plate-like substrate and having a length L and an interval D. When a sample (25) having and is prepared, the electric resistance R between the pair of measurement electrodes is measured, and the surface electric resistivity ρ represented by the following equation is calculated, the surface electric resistivity ρ is Any of claims 1 to 5, wherein the conductive portion is formed by using the conductive material having a temperature range of 100 to 500°C of 1.0 x 10 ^{7 to} 1.0 x 10 ¹⁰ Ω·cm. 2. The particulate matter detection sensor according to item 1.
ρ=R×L×T/D The conductive material is a ceramic having a perovskite structure whose molecular formula is represented by ABO ₃ , A is at least one selected from La, Sr, Ca and Mg, and B is Ti, Al and Zr. The particulate matter detection sensor according to any one of claims 1 to 6, which is at least one selected from Y and Y. 8. The particulate matter detection sensor according to claim 7, wherein the main component of A is Sr, the subcomponent is La, and the B is Ti. A particulate matter detection device (10) comprising: the particulate matter detection sensor according to any one of claims 1 to 8; and a control unit (7) electrically connected to the particulate matter detection sensor, The control unit, based on the measured value of the current, a voltage applying unit (71) that applies a voltage between the pair of electrodes, a current measuring unit (72) that measures the current flowing between the pair of electrodes, A particulate matter detection device comprising: a calculation unit (73) that calculates the amount of the particulate matter contained in the exhaust gas.

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