JP2020030102A - Fine particle sensor - Google Patents

Abstract

To provide a fine particle sensor such that an inner peripheral surface of a green compact is in contact with an outer peripheral surface of an insulation spacer so that none of gas to be measured passes between the inner peripheral surface of the green compact and the outer peripheral surface of the insulation spacer.SOLUTION: An insulation spacer 50 comprises an annular electric insulation film 55 which covers at least a part of an outer peripheral surface 51b of a main body part 51 entirely in a peripheral direction without any gap such that a terminal connection part is not covered and at least a part of a lead part is covered. At least a part of an inner peripheral surface 43c of a green compact 43 comes into contact with the electric insulation film 55 entirely in a peripheral direction so as to achieve airtight sealing between an outer peripheral surface 50b of the insulation spacer 50 and an inner peripheral surface 20c of outside metal fittings 20.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a particle sensor, and more particularly, to a particle sensor that detects particles contained in a gas to be measured flowing through a ventilation pipe.

  In an internal combustion engine (for example, a diesel engine), fine particles such as soot may be included in the exhaust gas. The exhaust gas containing such fine particles is collected and purified by a filter. Further, if necessary, a filter is heated to a high temperature to burn and remove fine particles accumulated in the filter. However, when a problem such as breakage of the filter occurs, unpurified exhaust gas is directly discharged downstream of the filter. Therefore, there is a need for a particle sensor capable of directly measuring the amount of fine particles in exhaust gas and detecting the amount of fine particles in exhaust gas in order to detect a failure of a filter.

  Such a particle sensor is disclosed, for example, in Patent Document 1. The fine particle sensor disclosed in Patent Document 1 is a fine particle sensor extending from the front end side to the rear end side in the axial direction, and a portion on the front end side of the fine particle sensor is set to a ground potential through which a gas to be measured containing fine particles flows. It is attached to the trachea and detects the amount of fine particles in the gas to be measured. This particle sensor includes a cylindrical outer fitting mounted on a ventilation pipe and set to a ground potential, and an inner fitting set to a first potential different from the ground potential and surrounded around the radial direction by the outer fitting.

International Publication No. WO 2016/027894

  Further, the particle sensor has a cylindrical shape extending in the axial direction, and includes an insulating spacer interposed between the inner metal fitting and the outer metal fitting to electrically insulate them. The insulating spacer has a gas contact portion located on the tip side of the insulating spacer and in contact with the gas to be measured, and a heater for heating the gas contact portion. Further, the fine particle sensor is an annular green compact obtained by compression-molding an electrically insulating powder, and is interposed between the outer peripheral surface of the insulating spacer and the outer metal fitting, and is provided between the outer peripheral surface of the insulating spacer and the outer metal fitting. A compact is provided that hermetically seals the space. Specifically, the inner peripheral surface of the green compact is pressed against the outer peripheral surface of the insulating spacer, and the outer peripheral surface of the green compact is pressed against the inner peripheral surface of the outer metal fitting. Is hermetically sealed.

  The insulating spacer includes a cylindrical spacer main body made of an electrically insulating ceramic and a sheet-like heater wound around the outer peripheral surface of the spacer main body. The sheet-shaped heater section includes a first ceramic sheet and a second ceramic sheet made of an electrically insulating ceramic, and a film-shaped heater interposed therebetween. The sheet-shaped heater is wound around the outer peripheral surface of the spacer body so that one end in the circumferential direction and the other end in the circumferential direction of the sheet-shaped heater do not overlap. Specifically, the sheet-shaped heater portion is wound around the outer peripheral surface of the spacer body such that one end in the circumferential direction and the other end in the circumferential direction are separated from each other, and has a C-shaped cross section.

  By the way, in the above-mentioned fine particle sensor, the green compact is in contact with the outer peripheral surface of the sheet-shaped heater portion, which is the outer peripheral surface of the insulating spacer. However, as described above, since the sheet-shaped heater portion is wound around the outer peripheral surface of the spacer main body in such a manner that one end in the circumferential direction and the other end in the circumferential direction are separated from each other, one end in the circumferential direction and the other end in the circumferential direction. A gap extending in the axial direction between the first and second portions. However, this gap cannot be filled with a part of the green compact (the inner peripheral surface portion), and the space between the outer peripheral surface of the insulating spacer and the outer metal fitting cannot be air-tightly sealed. there were. Specifically, the gas to be measured may pass through the gap between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer, and the gas to be measured may flow from the outside to the inside of the particle sensor. Was.

  Further, one end in the circumferential direction or the other end in the circumferential direction of the sheet-shaped heater portion wound around the outer peripheral surface of the spacer main body may be separated from the outer peripheral surface of the spacer main body. A minute gap (a gap extending in the axial direction) was sometimes formed between the other end in the circumferential direction and the outer peripheral surface of the spacer body. Since it is difficult to fill the minute gap with a part (the inner peripheral surface part) of the green compact, the green compact is used to hermetically seal (close) the outer peripheral surface of the insulating spacer and the outer fitting with the green compact. ) I couldn't do that. Specifically, the gas to be measured may pass between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer through the minute gap, and the gas to be measured may flow from the outside to the inside of the particle sensor. was there.

  The present invention has been made in view of such circumstances, and the inner peripheral surface of the green compact is formed so that the gas to be measured does not pass between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer. It is an object of the present invention to provide a fine particle sensor in contact with an outer peripheral surface of an insulating spacer.

  One embodiment of the present invention is a fine particle sensor extending from a front end side to a rear end side in an axial direction, and a portion of the front end side of the fine particle sensor is set to a ground potential through which a measurement target gas including fine particles flows. A particulate outer sensor attached to the ventilation pipe and configured to detect the amount of the particulates in the gas to be measured; It is set to a potential, and the inner metal member surrounded by the outer metal member in the radial direction is formed in a cylindrical shape extending in the axial direction, and is interposed between the inner metal member and the outer metal member to electrically insulate them. An insulating spacer having a gas contact portion in contact with the gas to be measured on the tip side in the axial direction thereof, and an annular green compact made of an electrically insulating powder, and an outer peripheral surface of the insulating spacer. The outer bracket And a green compact interposed between the inner peripheral surface and the insulating spacer, wherein the insulating spacer is a cylindrical main body made of electrically insulating ceramic, an electrically insulating ceramic sheet, and A heat generating sheet having a film-shaped heat generating resistor formed on a side surface thereof, wherein the heat generating sheet is wound around a portion of the outer peripheral surface of the main body portion on the tip side in the axial direction to heat the gas contact portion. A film-like lead formed on the outer peripheral surface of the main body, the lead being connected to the heating resistor and extending toward the rear end in the axial direction; and the outer peripheral surface of the main body. And a film-shaped terminal connection portion connected to the rear end of the lead portion, and without covering the terminal connection portion, covering at least a part of the lead portion, At least a part of the outer peripheral surface, An annular electrical insulating film that covers without gaps over the entire direction, wherein the green compact is located on the rear end side of the heat generating sheet in the axial direction and at least an inner peripheral surface of the green compact. A part is a fine particle sensor that is in contact with the electrical insulating film over the entire circumferential direction and hermetically seals a gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting.

  The above-described particle sensor has a cylindrical shape extending in the axial direction, and includes an insulating spacer interposed between the inner fitting and the outer fitting to electrically insulate the inner fitting and the outer fitting. The insulating spacer is formed on a cylindrical main body made of an electrically insulating ceramic, a heat generating sheet wound around a portion of the outer peripheral surface of the main body near the axial end, and an outer peripheral surface of the main body. And a film-like terminal connection formed on the outer peripheral surface of the main body and connected to the rear end of the lead. The heating sheet includes an electrically insulating ceramic sheet and a film-shaped heating resistor formed on the inner surface (inner peripheral surface) of the ceramic sheet. The heat generation sheet heats the “gas contact portion of the insulating spacer that is located on the distal end side in the axial direction and contacts the gas to be measured”.

  By the way, if foreign matter such as soot contained in the gas to be measured adheres to the gas contact portion of the insulating spacer, the insulating property of the surface of the gas contact portion decreases. As a result, the insulation between the inner metal fitting at the first potential and the outer metal fitting at the ground potential is reduced. If fine particle detection is performed by the fine particle sensor in such a state, the amount of fine particles in the gas to be measured may not be properly detected.

  On the other hand, in the above-described particle sensor, the insulating spacer has the heating sheet for heating the gas contact portion. Therefore, even when foreign matter such as soot contained in the gas to be measured adheres to the gas contact portion of the insulating spacer, the soot adhering to the surface of the gas contact portion is heated by heating the gas contact portion with the heating sheet. Foreign matter such as can be removed. Thus, the insulation between the inner metal fitting at the first potential and the outer metal fitting at the ground potential can be restored, and the amount of fine particles in the gas to be measured can be appropriately detected.

  Further, the above-mentioned fine particle sensor is an annular green compact made of an electrically insulating powder (for example, ceramic powder such as talc), and is interposed between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. And a green compact for hermetically sealing (sealing) the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. Specifically, the inner peripheral surface of the green compact is pressed against the outer peripheral surface of the insulating spacer, and the outer peripheral surface of the green compact is pressed against the inner peripheral surface of the outer metal fitting. The space between the inner peripheral surface and the inner peripheral surface is hermetically sealed. This green compact is located on the rear end side of the heat generating sheet of the insulating spacer in the axial direction.

  That is, in the above-described fine particle sensor, the compact is interposed between the insulating spacer and the outer metal fitting in such a manner that the green compact is brought into contact with a portion of the outer peripheral surface of the insulating spacer located closer to the rear end side than the heat generating sheet. The space between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting is hermetically sealed. For this reason, the heat generating sheet is wound around the outer peripheral surface of the main body in such a manner that one end in the circumferential direction and the other end in the circumferential direction of the heat generating sheet are separated from each other. Even in the case where there is a gap extending in the axial direction, the above-described fine particle sensor does not need to fill the gap with a compact to make it airtight. Further, one end in the circumferential direction or the other end in the circumferential direction of the heating sheet is peeled off from the outer peripheral surface of the main body, and between the one end in the circumferential direction or the other end in the circumferential direction and the outer peripheral surface of the main body. Even when a minute gap is formed, the above-described fine particle sensor does not need to fill the minute gap with a compact to make it airtight.

Further, in the above-described particle sensor, at least a part (a part in the axial direction) of the outer peripheral surface of the main body part is formed in such a manner that the insulating spacer covers at least a part of the lead part without covering the terminal connection part. It has an annular electrical insulating film that covers the entire circumferential direction without gaps.
Further, at least a part (part in the axial direction) of the inner peripheral surface of the green compact is in contact with the electric insulating film (the outer peripheral surface) over the entire circumferential direction of the outer peripheral surface of the insulating spacer. The body presses the electrical insulating film in a manner of pressing it radially inward) to hermetically seal the gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting.

  Accordingly, in the above-described fine particle sensor, the inner peripheral surface of the green compact is formed over the entire outer peripheral surface of the insulating spacer in the circumferential direction with respect to the outer peripheral surface of the insulating spacer (specifically, the outer peripheral surface of the electric insulating film). Contact can be made without a gap (specifically, there is no gap between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer so that the gas to be measured passes in the axial direction between the two). Therefore, in the above-described fine particle sensor, the inner peripheral surface of the green compact was in contact with the outer peripheral surface of the insulating spacer so that the gas to be measured did not pass between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer. It becomes a particle sensor. Eventually, the compact between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer bracket hermetically seals (closes) the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer bracket. It becomes a particle sensor.

In addition, as the electric insulating film, for example, a sprayed film of an electric insulating ceramic, an electric insulating glass film, or the like can be given.
Examples of the film-shaped lead portion include those formed by directly printing on the outer peripheral surface of the main body portion by, for example, inkjet printing or tampo printing.

  Further, in the above-mentioned particle sensor, it is preferable that the thickness of the electric insulating film is smaller than the thickness of the ceramic sheet.

  In the above-described fine particle sensor, the thickness of the electric insulating film is smaller than the thickness of the ceramic sheet. For this reason, the heat capacity of the insulating spacer can be reduced as compared with the case where the thickness of the electric insulating film is equal to or greater than the thickness of the ceramic sheet. Therefore, in the above-described particle sensor, an electric insulating film is provided on the outer peripheral surface of the main body in order to hermetically seal the outer peripheral surface of the insulating spacer and the outer metal fitting. (Specifically, a decrease in the rate of temperature rise of the gas contact portion due to heating of the heat generating sheet) can be suppressed.

  Another aspect of the present invention is a fine particle sensor extending from the front end side to the rear end side in the axial direction, wherein a portion on the front end side of the fine particle sensor is set to a ground potential through which a measurement target gas including fine particles flows. In the fine particle sensor attached to the ventilation pipe, which detects the amount of the fine particles in the gas to be measured, a cylindrical outer fitting attached to the ventilation pipe and set to the ground potential, and the ground potential is A first potential different from that of the first metal member, the inner metal member surrounded by the outer metal member in a radial direction, and a cylindrical shape extending in the axial direction. The inner metal member and the outer metal member are interposed between and electrically connected to each other. An insulating spacer having a gas contact portion in contact with the gas to be measured on its tip side in the axial direction, and an annular green compact made of an electrically insulating powder, Outer peripheral surface and said And a compact interposed between the inner peripheral surface of the side fitting and the inner spacer, wherein the insulating spacer is a cylindrical main body made of electrically insulating ceramic, and the axial line of the outer peripheral surface of the main body. A heating resistor for heating the gas contact portion, and a film-like lead formed on the outer peripheral surface of the main body. A lead portion connected to the heating resistor and extending toward the rear end side in the axial direction; and a film-shaped terminal connection formed on the outer peripheral surface of the main body portion and connected to the rear end portion of the lead portion. A portion that covers at least a portion of the lead portion without covering the terminal connection portion, and that covers at least a portion of the outer peripheral surface of the main body portion with no gap over the entire circumferential direction. An electrical insulating film; A part is a fine particle sensor that is in contact with the electric insulating film over the entire circumferential direction and hermetically seals the gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. .

  The above-described particle sensor has a cylindrical shape extending in the axial direction, and includes an insulating spacer interposed between the inner fitting and the outer fitting to electrically insulate the inner fitting and the outer fitting. The insulating spacer includes a cylindrical main body made of an electrically insulating ceramic, a film-shaped heating resistor formed at a portion of the outer peripheral surface of the main body near the axial end, and an outer periphery of the main body. It has a film-shaped lead portion formed on the surface and a film-shaped terminal connection portion formed on the outer peripheral surface of the main body and connected to the rear end of the lead portion. The lead portion is connected to the heating resistor and extends toward the rear end in the axial direction.

  The heating resistor of the insulating spacer heats the “gas contact portion of the insulating spacer that is located at the distal end side in the axial direction and contacts the gas to be measured”. For this reason, in the above-described fine particle sensor, even when foreign matter such as soot contained in the gas to be measured adheres to the gas contact portion of the insulating spacer, the gas contact portion is heated by the heat generating resistor, and the surface of the gas contact portion is heated. Foreign matter such as soot adhering to the surface can be removed. Thus, the insulation between the inner metal fitting at the first potential and the outer metal fitting at the ground potential can be restored, and the amount of fine particles in the gas to be measured can be appropriately detected.

  Further, the above-mentioned fine particle sensor is an annular green compact made of an electrically insulating powder (for example, ceramic powder such as talc), and is interposed between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. And a green compact for hermetically sealing (sealing) the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. Specifically, the inner peripheral surface of the green compact is pressed against the outer peripheral surface of the insulating spacer, and the outer peripheral surface of the green compact is pressed against the inner peripheral surface of the outer metal fitting. The space between the inner peripheral surface and the inner peripheral surface is hermetically sealed.

Further, in the above-described particle sensor, at least a part (a part in the axial direction) of the outer peripheral surface of the main body part is formed in such a manner that the insulating spacer covers at least a part of the lead part without covering the terminal connection part. It has an annular electrical insulating film that covers the entire circumferential direction without gaps.
Further, at least a part (part in the axial direction) of the inner peripheral surface of the green compact is in contact with the electric insulating film (the outer peripheral surface) over the entire circumferential direction of the outer peripheral surface of the insulating spacer. The body presses the electrical insulating film in a manner of pressing it radially inward) to hermetically seal the gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting.

  Accordingly, in the above-described fine particle sensor, the inner peripheral surface of the green compact is formed over the entire outer peripheral surface of the insulating spacer in the circumferential direction with respect to the outer peripheral surface of the insulating spacer (specifically, the outer peripheral surface of the electric insulating film). Contact can be made without a gap (specifically, there is no gap between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer so that the gas to be measured passes in the axial direction between the two). Therefore, in the above-described fine particle sensor, the inner peripheral surface of the green compact was in contact with the outer peripheral surface of the insulating spacer so that the gas to be measured did not pass between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer. It becomes a particle sensor. Eventually, the space between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting is hermetically sealed (sealed) by the green compact interposed between the outer peripheral face of the insulating spacer and the inner peripheral face of the outer fitting. It becomes a particle sensor.

In addition, as the electric insulating film, for example, a sprayed film of an electric insulating ceramic, an electric insulating glass film, or the like can be given.
Examples of the film-shaped heating resistor and the film-shaped lead portion include those formed by directly printing on the outer peripheral surface of the main body portion by, for example, inkjet printing or tampo printing.

  Further, in the above-mentioned particle sensor, it is preferable that the thickness of the electric insulating film is smaller than the thickness of the main body.

  In the above-described fine particle sensor, in the insulating spacer, the thickness of the electric insulating film is smaller than the thickness of the main body. Therefore, the heat capacity of the insulating spacer can be reduced as compared with the case where the thickness of the electric insulating film is equal to or greater than the thickness of the main body. Therefore, in the above-described particle sensor, an electric insulating film is provided on the outer peripheral surface of the main body in order to airtightly seal between the outer peripheral surface of the insulating spacer and the outer metal fitting. (Specifically, a decrease in the rate of temperature rise of the gas contact portion due to heating of the heating resistor) can be reduced.

  Further, in any one of the particle sensors described above, the heating resistor may be a particle sensor covered with the electrical insulating film without being exposed on an outer peripheral surface of the insulating spacer.

  As described above, the heating resistor is located on the distal end side in the axial direction of the insulating spacer. However, the portion of the insulating spacer on the distal end side in the axial direction is a gas contact portion that contacts the gas to be measured. Therefore, if the heating resistor is exposed on the outer peripheral surface of the insulating spacer, the soot contained in the gas to be measured is formed on the surface of the heating resistor and around the heating resistor (the outer peripheral surface of the main body). There is a possibility that the heat generating resistor may be short-circuited due to the adhesion of foreign matter such as.

  On the other hand, in the above-described fine particle sensor, the heating resistor is covered with the electrical insulating film without being exposed on the outer peripheral surface of the insulating spacer. This can prevent foreign matter such as soot contained in the gas to be measured from adhering to the surface of the heating resistor and around the heating resistor (the outer peripheral surface of the main body).

  Further, in any of the particle sensors described above, it is preferable that the electric insulating film is a particle sensor that is a sprayed film of an electrically insulating ceramic.

  In the above-described fine particle sensor, the electric insulating film is formed by a sprayed film of an electric insulating ceramic. Since the sprayed film of the electrically insulating ceramic is a dense ceramic film, the hermeticity (sealability) between the sprayed film and the inner peripheral surface of the green compact is improved. This ensures that the gas to be measured does not pass between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer.

  Further, in any one of the particle sensors, it is preferable that the entire inner peripheral surface of the green compact is in contact with the electric insulating film.

  In the above-described fine particle sensor, the entire inner peripheral surface of the green compact is in contact with the electric insulating film. In other words, all of the outer peripheral surfaces of the insulating spacer that come into contact with the inner peripheral surface of the green compact are outer peripheral surfaces of the electric insulating film. With this configuration, it is possible to prevent the film-shaped lead formed on the outer peripheral surface of the main body from coming into contact with the green compact. Accordingly, it is possible to prevent the lead portion from being damaged due to the contact with the green compact.

FIG. 2 is a diagram illustrating an example in which a particle sensor is mounted on an exhaust pipe of an engine of a vehicle. FIG. 2 is a longitudinal sectional view of the particle sensor according to the first embodiment. It is an expanded sectional view showing connection of a discharge element in a separator of the same particulate sensor. FIG. 2 is a longitudinal sectional view of the particle sensor, which is a longitudinal sectional view at a position shifted by 90 degrees around an axis from FIG. 2. FIG. 3 is an exploded perspective view of the particle sensor. FIG. 2 is a perspective view of the discharge element according to the first embodiment. It is an exploded perspective view of the same discharge element. FIG. 2 is a diagram illustrating a circuit configuration of a control device of the particle detection system according to the first embodiment. FIG. 2 is a perspective view of an insulating spacer with a heater according to the first embodiment. FIG. 3 is an exploded perspective view showing a developed heat generating sheet of the insulating spacer with a heater. FIG. 3 is an enlarged view of a portion B in FIG. 2. FIG. 3 is an explanatory diagram of the particle sensor according to the first embodiment. FIG. 7 is a vertical sectional view of a particle sensor according to a second embodiment. FIG. 13 is a longitudinal sectional view of the particle sensor, and is a longitudinal sectional view of FIG. 13 at a position shifted by 90 degrees around the axis. FIG. 3 is an exploded perspective view of the particle sensor. FIG. 9 is a perspective view of an insulating spacer with a heater according to a second embodiment. FIG. 9 is a perspective view of an insulating spacer main body with a heater according to a second embodiment. FIG. 9 is a diagram illustrating an electric insulating film according to a first modification.

(Example 1)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram illustrating an example in which the particle sensor 10 according to the first embodiment is mounted on an exhaust pipe EP of an engine ENG mounted on a vehicle AM. FIG. 2 is a longitudinal sectional view of the particle sensor 10 according to the first embodiment. FIG. 3 is an enlarged longitudinal sectional view showing the connection between the discharge element 60, the discharge potential cable 82, and the element heater leads 84 and 86 in the separators 75 and 76 in the particle sensor 10. FIG. 4 is an enlarged cross-sectional view of the particle sensor 10, and is a vertical cross-sectional view cut at a position shifted by 90 degrees around the axis from FIG. FIG. 5 is an exploded perspective view of the particle sensor 10. FIG. 6 is a perspective view of the discharge element 60 included in the particle sensor 10. FIG. 7 is an exploded perspective view of the discharge element 60. FIG. 8 is a diagram illustrating a circuit configuration of the control device 100 of the particle detection system 1 according to the first embodiment.

  In this specification, as shown in FIG. 2 and the like, the protector 31 (gas intake / discharge) in the axial direction GH (the direction in which the axis AX extends, the vertical direction in FIG. 2) along the axis AX of the particle sensor 10 is used. The side on which the tube is disposed (lower in FIG. 2) is referred to as a front end GS, and the opposite side (upper in FIG. 2) on which the discharge potential cable 82 or the like extends is referred to as a rear end GK. Further, an outward direction in the radial direction with respect to the axis AX (outward in the left and right direction in FIG. 2) is defined as a radially outer DO, and an inward direction (inward in the left and right direction in FIG. 2) is defined as a radially inner DI.

  As shown in FIG. 1, a particle detection system 1 (hereinafter, also simply referred to as a system 1) of the first embodiment includes a particle sensor 10 and a control device 100 that controls the particle sensor 10. Among them, the particle sensor 10 is mounted on an exhaust pipe EP (vent pipe) of an engine ENG (internal combustion engine) mounted on the vehicle AM, and detects soot and the like in exhaust gas EG (gas to be measured) flowing through the exhaust pipe EP. The fine particles S are detected. More specifically, the particle sensor 10 is fixed to a metal exhaust pipe EP, and a part of the tip side GS is disposed in the exhaust pipe EP and is exposed to the exhaust gas EG (see FIG. 12).

  The control device 100 is connected to the particle sensor 10 via the discharge potential cable 82, the element heater leads 84 and 86, and the spacer heater leads 92 and 94 (FIGS. 1 to 4 and FIG. 4). , FIG. 8). Among them, the discharge potential cable 82 is a coaxial cable, and the discharge potential lead wire 82L of the core wire (center conductor) is set to the discharge potential DV (see FIG. 8). On the other hand, the element heater lead wires 84 and 86 and the spacer heater lead wires 92 and 94 are thin, single-core, insulated wires. The discharge potential cable 82 has a chassis ground potential CGND (ground potential) and is surrounded by a braided tube 23 in which a thin metal wire is braided in a tubular shape.

  The control device 100 has an ion source power supply circuit 110 and a measurement control circuit 120 as shown in FIG. The ion source power supply circuit 110 has a first output terminal 111 at a sensor ground potential SGND (first potential) and a second output terminal 112 at a discharge potential DV. The second output terminal 112 is connected to a discharge potential lead wire 82L which is a core wire of the discharge potential cable 82. The discharge potential DV is a half-wave rectified positive high potential (for example, 1 to 2 kV) based on the sensor ground potential SGND. The output current of the ion source power supply circuit 110 is feedback-controlled, and constitutes a constant current power supply whose effective value is a predetermined current value (for example, 5 μA). The ion source power supply circuit 110 generates a discharge potential DV to be applied to a discharge electrode body 62 (see FIGS. 2, 6, and 7) of the discharge element 60 described later.

  On the other hand, the measurement control circuit 120 includes a signal current detection circuit 140, an element heater control circuit 150, and a spacer heater control circuit 160, as shown in FIG. Among them, the signal current detection circuit 140 has a first input terminal 141 set to a sensor ground potential SGND and a second input terminal 142, and a signal input between the first input terminal 141 and the second input terminal 142. Is detected. The sensor ground potential SGND is higher than the chassis ground potential CGND (ground potential) by an offset voltage Voffset (specifically, 0.5 V).

  The element heater control circuit 150 is a circuit that controls energization to an element heater wiring 64 (see FIG. 7) incorporated in the discharge element 60 described below by PWM control. The element heater control circuit 150 has a first output terminal 151 connected to the element heater lead 84 and a second output terminal 152 connected to the element heater lead 86. The second output terminal 152 and the element heater lead 86 are electrically connected to the chassis ground potential CGND. The first output terminal 151 and the element heater lead 84 are set to the element heater potential EHV (see FIG. 8).

  The spacer heater control circuit 160 is a circuit that controls the energization of a spacer heater 50B (see FIGS. 4 and 9) of the insulating spacer 50 with a heater, which will be described later, by PWM control. The spacer heater control circuit 160 has a first output terminal 161 connected to the spacer heater lead wire 92 and a second output terminal 162 connected to the spacer heater lead wire 94. The second output terminal 162 and the spacer heater lead 94 are electrically connected to the chassis ground potential CGND. The first output terminal 161 and the spacer heater lead wire 92 are set to the spacer heater potential SHV (see FIG. 8).

  Further, the ion source power supply circuit 110 is surrounded by an inner circuit case 170 which is set to the sensor ground potential SGND. The first output terminal 111 of the ion source power supply circuit 110, the first input terminal 141 of the signal current detection circuit 140, and the secondary core 131B of the insulating transformer 130 are electrically connected to the inner circuit case 170. Note that the first output terminal 111 of the ion source power supply circuit 110 is electrically connected to the outer conductor 82D of the discharge potential cable 82 (see FIG. 8).

  The insulating transformer 130 is a transformer in which the primary side and the secondary side are insulated, and the iron core 131 has a primary iron core 131A wound with a primary coil 132 and a secondary iron core wound with a secondary coil 133. 131B. Of these, the primary iron core 131A is electrically connected to the chassis ground potential CGND. On the other hand, as described above, the secondary core 131B is electrically connected to the sensor ground potential SGND (the first output terminal 111 of the ion source power supply circuit 110) (see FIG. 8).

  Further, the measurement control circuit 120 including the signal current detection circuit 140, the element heater control circuit 150, and the spacer heater control circuit 160, the ion source power supply circuit 110, the inner circuit case 170, and the insulating transformer 130 are connected to the chassis ground potential CGND and Is surrounded by an outer circuit case 180. Further, the second input terminal 142 of the signal current detection circuit 140, the second output terminal 152 of the element heater control circuit 150, the second output terminal 162 of the spacer heater control circuit 160, and the primary core 131A of the insulating transformer 130 are: The outer circuit case 180 is connected to the chassis ground potential CGND. In addition, the outer circuit case 180 is electrically connected to the braided tube 23 surrounding the discharge potential cable 82 (see FIG. 8).

  The measurement control circuit 120 has a built-in regulator power supply PS for supplying a predetermined DC voltage. The regulator power supply PS is connected to an external battery BT mounted on the vehicle AM via a power supply line BC, and is driven by the battery BT. One end of the battery BT is connected to a chassis ground potential CGND. The measurement control circuit 120 includes a microprocessor 122 and can communicate with an electronic control unit ECU that controls the engine ENG via a communication line CC. Thus, a signal such as the measurement result (the magnitude of the signal current Is) of the signal current detection circuit 140 described above can be transmitted to the electronic control unit ECU (see FIG. 8).

  In addition, part of the power input from the external battery BT to the measurement control circuit 120 through the regulator power supply PS is distributed to the ion source power supply circuit 110 via the insulating transformer 130. In the insulating transformer 130, a primary coil 132 forming a part of the measurement control circuit 120, a secondary coil 133 forming a part of the ion source power supply circuit 110, and an iron core 131 (primary iron core 131A, secondary iron core 131A). The side iron core 131B) is electrically insulated from each other. Therefore, while electric power is distributed from the measurement control circuit 120 to the ion source power supply circuit 110, electrical insulation between them can be maintained.

Next, the particle sensor 10 according to the first embodiment will be described in detail.
As shown in FIGS. 2 to 4, the fine particle sensor 10 has a straight rod shape extending in the axial direction GH. The particle sensor 10 includes a discharge element 60, an inner fitting 30, and an outer fitting 20. Among them, the discharge element 60 is aerial discharge (specifically, between the needle-shaped electrode part 62D protruding at the element tip part 60S of the discharge element 60 and the protector 31 of the inner fitting 30 as described later. (Corona discharge) to generate ions CP.

Further, the inner metal fitting 30 is kept at the sensor ground potential SGND (first potential) while securing electrical insulation from the discharge element 60 while holding the discharge element 60. The inner fitting 30 surrounds the discharge element 60 with a conductor to form a Faraday cage.
Further, the outer fitting 20 has a cylindrical shape, and holds the inner fitting 30 around the radial direction periphery of the inner fitting 30 while securing electrical insulation with the inner fitting 30. The outer metal fitting 20 is attached to the exhaust pipe EP and has a chassis ground potential CGND (ground potential) different from the sensor ground potential SGND.

  The inner fitting 30 includes a protector 31, a conductive seal body 37, a second inner cylinder 38, and a first inner cylinder 39, which will be described later. The outer fitting 20 includes a mounting fitting 21, an outer cylinder 22, a braided tube 23, and a braid holding fitting 24, which will be described later.

  More specifically, the particle sensor 10 includes a cylindrical mounting member 21 on its own distal end GS. The mounting bracket 21 has a tool engaging portion 21H which bulges radially outward to form a hexagonal outer shape. Further, the mounting bracket 21 has a cylindrical wall 21W surrounding the outer periphery of a protector 31 (gas inlet / outlet pipe) to be described later, at a position on the tip side GS with respect to the tool engaging portion 21H. On the outer periphery of the cylindrical wall portion 21W, a male screw portion 21N for fixing the particle sensor 10 to the exhaust pipe EP is formed. Accordingly, the particle sensor 10 is fixed to the exhaust pipe EP by using the male screw portion 21N of the mounting bracket 21 via a metal mounting boss (not shown) separately provided on the exhaust pipe EP. For this reason, the mounting bracket 21 has the same chassis ground potential CGND as the exhaust pipe EP.

Further, a metal outer cylinder 22 is fixedly provided on the rear end side GK of the mounting bracket 21. Specifically, the front end 22S of the outer cylinder 22 is externally fitted to the rear end 21K of the mounting bracket 21, and the mounting bracket 21 and the outer cylinder 22 are integrated by laser welding them.
Further, the rear end 22K of the rear end side GK of the outer cylinder 22 is configured to be smaller in diameter than the front end 22S. A grommet 46 made of insulating rubber is fitted inside the rear end 22K of the outer cylinder 22, and a braided tube 23 made of a metal wire is fitted outside the rear end 22K. A tubular braid holding fitting 24 is covered. These are caulked radially inward, so that the grommet 46, the braided tube 23, and the braid holding fitting 24 are held by the rear end 22K of the outer cylinder 22.

For this reason, by attaching the mounting bracket 21 of the particle sensor 10 to the exhaust pipe EP, the mounting bracket 21 and the outer cylinder 22, the braided tube 23, and the braid holding bracket 24 that are connected to the mounting bracket 21 are set to the chassis ground potential CGND. You.
The grommet 46 has a discharge potential cable 82, element heater leads 84 and 86, and spacer heater leads 92 and 94 inserted therein.

  A cylindrical heater is provided on a radially inner side DI of the mounting bracket 21 via an insulating holder 42 made of insulating ceramic, a talc compact 43, an insulating sleeve 44 made of insulating ceramic, and a wire packing 45. Attached insulating spacer 50 is held. The insulating holder 42, the talc compact 43, the insulating sleeve 44, and the wire packing 45 are compressed in the axial direction GH by caulking and bending the rear end 21KK of the mounting bracket 21 to the radially inner side DI. .

  The talc green compact 43 is an annular green compact obtained by compression-molding talc powder having electrical insulation properties. As shown in FIGS. 2 and 4, the talc compact 43 is interposed between the outer peripheral surface 50 b of the insulating spacer with heater 50 described later and the inner peripheral surface 21 c of the mounting bracket 21 of the outer bracket 20. Then, the space between the outer peripheral surface 50b of the insulating spacer with heater 50 and the inner peripheral surface 21c of the mounting bracket 21 of the outer bracket 20 is hermetically sealed.

  In detail, as described above, by crimping and bending the rear end 21KK of the mounting bracket 21 to the radially inner side DI, the talc green compact 43 is compressed in the axial direction GH and simultaneously to the radially outer side DO. By deforming so as to increase the diameter, the inner peripheral surface 43c of the talc green compact 43 comes into pressure contact (close contact) with the outer peripheral surface 50b of the insulating spacer 50 with a heater, and the outer peripheral surface 43b of the talc green compact 43 becomes The inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21) is pressed (closely adhered) to the outer peripheral surface 50b of the insulating spacer 50 with a heater and the inner peripheral surface 20c of the outer bracket 20. Is hermetically sealed (sealed).

  In addition, a first inner cylinder 39 and a second inner cylinder 38 are arranged on the radially inner side DI of the outer cylinder 22 in addition to the insulating spacer 50 with a heater (see FIGS. 2 and 4). The first inner cylinder 39 has a cylindrical shape, and surrounds the element rear end side portion 60K of the rear end side GK of the discharge element 60. As shown in FIGS. 2 and 4, the insulating spacer with heater 50 has a cylindrical shape extending in the axial direction GH, and is interposed between the inner metal fitting 30 and the outer metal fitting 20 to form the inner metal fitting 30 and the outer metal fitting. 20 is electrically insulated. The insulating spacer with heater 50 is located at the tip side GS of the insulating spacer with heater 50 and is in contact with the exhaust gas EG (gas to be measured), and a spacer heater that heats the gas contact portion 50S. 50B (more specifically, a heat generation sheet 52 described later).

  Here, the insulating spacer with heater 50 (insulating spacer) of the first embodiment will be described in detail. As shown in FIG. 9, the insulating spacer with heater 50 includes a cylindrical spacer main body 51 (main body) and a heat generating sheet wound around a portion of the outer peripheral surface 51 b of the spacer main body 51 on the distal end side GS in the axial direction GH. 52. The heat generating sheet 52 is wound around the outer peripheral surface 51b of the spacer body 51 in such a manner that one end 52b in the circumferential direction and the other end 52c in the circumferential direction are separated from each other, and one end 52b in the circumferential direction and the other end in the circumferential direction. A gap G extending in the axial direction GH is provided between the gap G and the gap 52c (see FIG. 9).

  Further, the insulating spacer with heater 50 includes a film-like lead portion (a first heater lead portion 56 and a second heater lead portion 57) formed on the outer peripheral surface 51b of the spacer main body 51 and the outer peripheral surface 51b of the spacer main body 51. Of these, a film-shaped terminal connection portion (first terminal connection portion 58 and second terminal connection portion 59) formed at a portion on the rear end side GK in the axial direction GH is provided.

The spacer body 51 is made of an electrically insulating ceramic (specifically, alumina) and has a cylindrical shape extending in the axial direction GH.
As shown in FIGS. 9 and 10, the heat generation sheet 52 includes an electrically insulating ceramic sheet 53 (specifically, a ceramic sheet made of alumina) and an inner side surface 53 c of the ceramic sheet 53 (the spacer body 51). (A surface in contact with the outer peripheral surface 51b). The heat generation sheet 52 is disposed on the tip side GS of the particle sensor 10 with respect to the axial direction GH with respect to the insulating holder 42 (see FIGS. 2 and 4). FIG. 10 is an exploded perspective view in which the heat generation sheet 52 is developed.

  The heating resistor 54 has a meandering (zigzag) shape and has a form extending in the circumferential direction CD of the insulating spacer with heater 50 (see FIGS. 9 and 10). As shown in FIG. 9, the first connecting portion 54b located on one side CD1 and the second connecting portion 54c located on the other side CD2 of the heating resistor 54 are formed on the outer peripheral surface 51b of the spacer body 51. By being wound, they are arranged close to each other in the circumferential direction CD.

  The heating resistor 54 comes into contact with a portion of the outer peripheral surface 51b of the spacer main body 51 located on the distal end side GS in the axial direction GH in a state where the heat generating sheet 52 is wound around the outer peripheral surface 51b of the spacer main body 51 (FIG. 9). More specifically, the first connection portion 54b of the heating resistor 54 contacts (electrically connects) the tip of a first heater lead portion 56 described later, and the second connection portion 54c is described later. The tip of the second heater lead portion 57 is contacted (electrically connected). By causing the heating resistor 54 to generate heat, the gas contact portion 50S of the insulating spacer with heater 50 can be heated.

  In the insulating spacer with heater 50 of the first embodiment, the heat generating sheet 52 (heat generating resistor 54), the first heater lead portion 56 and the second heater lead portion 57, the first terminal connecting portion 58 and the second terminal The connection portion 59 forms a spacer heater 50B. The spacer main body 51, the heat generation sheet 52, the first heater lead portion 56 and the second heater lead portion 57, and the first terminal connection portion 58 and the second terminal connection portion 59 form the insulating spacer main body portion 50 A with a heater. Is composed.

  When foreign matter such as soot contained in the exhaust gas EG (gas to be measured) adheres to the gas contact portion 50S of the insulating spacer 50 with a heater, the electric insulation of the surface of the gas contact portion 50S decreases. Thus, the electrical insulation between the inner metal fitting 30 at the sensor ground potential SGND (first potential) and the outer metal fitting 20 at the chassis ground potential CGND (ground potential) is reduced. If the fine particle sensor 10 performs fine particle detection in such a state, the amount of fine particles in the exhaust gas EG may not be properly detected.

  On the other hand, in the particle sensor 10 of the first embodiment, as described above, the insulating spacer with heater 50 has the spacer heater 50B (the heating resistor 54) for heating the gas contact portion 50S. Therefore, even when foreign matter such as soot contained in the exhaust gas EG adheres to the gas contact portion 50S of the insulating spacer 50 with a heater, the gas contact portion 50S is heated by the spacer heater 50B (the heating resistor 54). Foreign matter such as soot adhering to the surface of the gas contact portion 50S can be removed. As a result, the electrical insulation between the inner metal fitting 30 at the sensor ground potential SGND (first potential) and the outer metal fitting 20 at the chassis ground potential CGND (ground potential) is restored, and the exhaust gas EG in the exhaust gas EG is restored. It is possible to appropriately detect the amount of the fine particles.

  When the heating sheet 52 is wound around the outer peripheral surface 51 b of the spacer body 51, the heating resistor 54 is not exposed on the outer peripheral surface 50 b of the insulating spacer with heater 50 and is covered with the ceramic sheet 53. (See FIG. 9). This prevents foreign matter such as soot contained in the exhaust gas EG (gas to be measured) from adhering to the surface of the heating resistor 54 and around the heating resistor 54 when the particle sensor 10 is used. In addition, it is possible to prevent the heating resistor 54 from being short-circuited through the foreign matter.

  The first heater lead portion 56 (lead portion) is made of a film-like conductor, and its tip (the portion located on the tip side GS in the axial direction GH) is formed of the heating resistor 54 as shown in FIG. It is connected to the first connection portion 54b and has a shape extending to the rear end side GK in the axial direction GH. The second heater lead portion 57 is formed of a film-shaped conductor, and its tip (a portion located on the tip side GS in the axial direction GH) is connected to the second connection portion 54c of the heating resistor 54 as shown in FIG. Connected to form a shape extending toward the rear end side GK in the axial direction GH. The first heater lead portion 56 and the second heater lead portion 57 are separated from each other in the circumferential direction CD of the spacer body 51.

  The first terminal connection portion 58 is formed of a film-shaped conductor, and is provided at a rear end portion 56b (a portion located on the rear end side GK in the axial direction GH) of the first heater lead portion 56 as shown in FIG. Connected. The second terminal connection portion 59 is made of a film-shaped conductor, and is connected to a rear end portion 57b (a portion located on the rear end side GK in the axial direction GH) of the second heater lead portion 57, as shown in FIG. ing.

  In the first embodiment, the first heater lead portion 56, the second heater lead portion 57, the first terminal connection portion 58, and the second terminal connection portion 59 are integrally formed on the outer peripheral surface 51b of the spacer body 51. Has formed. Specifically, a conductor (metal fine particles) is printed in a film shape on the outer peripheral surface 51b of the spacer body 51 by inkjet printing or tampo printing, so that the first heater lead portion 56, the second heater lead portion 57, and the One terminal connection part 58 and second terminal connection part 59 are formed.

  By the way, in the conventional fine particle sensor, the talc green compact is in contact with the outer peripheral surface of the sheet-shaped heater portion which is the outer peripheral surface of the insulating spacer with the heater. Furthermore, since the sheet-shaped heater is wound around the outer peripheral surface of the spacer body in a manner that one end in the circumferential direction and the other end in the circumferential direction are separated from each other, similarly to the heating sheet 52 of the first embodiment, There was a gap extending in the axial direction between one end in the direction and the other end in the circumferential direction. However, this gap cannot be filled with a part of the talc compact (the inner peripheral surface portion), and the space between the outer peripheral surface of the insulating spacer with heater and the outer metal fitting is airtightly sealed (sealed). There was something I couldn't do. Specifically, the gas to be measured may pass through the gap between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer with a heater, and the gas to be measured may flow from the outside to the inside of the particle sensor. was there.

  Further, one end in the circumferential direction or the other end in the circumferential direction of the sheet-shaped heater portion wound around the outer peripheral surface of the spacer main body may be separated from the outer peripheral surface of the spacer main body. A minute gap was sometimes formed between the other end in the circumferential direction and the outer peripheral surface of the spacer body. However, since it is difficult to fill the minute gap with a part (inner peripheral portion) of the talc compact, the compact between the outer peripheral surface of the insulating spacer with the heater and the outer fitting is airtight. In some cases, sealing (sealing) could not be performed. Specifically, the gas to be measured passes between the inner peripheral surface of the green compact and the outer peripheral surface of the insulating spacer with the heater through the minute gap, and the gas to be measured flows from the outside to the inside of the particle sensor. There was a risk of doing so.

  On the other hand, in the fine particle sensor 10 of the first embodiment, the talc compact 43 is disposed on the rear end side GK of the insulating spacer 50 with heater in the axial direction GH with respect to the heating sheet 52 (see FIG. 2 and FIG. 2). (See FIG. 4). That is, the talc compact 43 is brought into contact with a portion of the outer peripheral surface 50b of the insulating spacer 50 with the heater located on the rear end side GK of the heating sheet 52 with respect to the outer peripheral surface 50b of the insulating spacer 50 with the heater. It is interposed between the metal fitting 20 (specifically, the inner peripheral surface 21c of the mounting metal 21) to hermetically seal the space therebetween.

  For this reason, in the particle sensor 10 of the first embodiment, as shown in FIG. 9, the heat generating sheet 52 is formed such that one end 52 b in the circumferential direction and the other end 52 c in the circumferential direction of the heat generating sheet 52 are separated from each other. Even if there is a gap G wound around the outer peripheral surface 51b of the 51 and extending in the axial direction GH, it is not necessary to fill the gap G with the talc compact 43 to make it airtight. Further, one end 52b or the other end 52c in the circumferential direction of the heat generating sheet 52 is peeled off from the outer peripheral surface 51b of the spacer body 51, and the one end 52b or the other end 52c in the circumferential direction is separated from the spacer body 51. Even when a minute gap is formed between the outer peripheral surface 51b and the outer peripheral surface 51b, there is no need to fill the minute gap with the talc compact 43 to make it airtight.

  Furthermore, in the particle sensor 10 of the first embodiment, the insulating spacer with heater 50 covers at least a part of the outer peripheral surface 51b of the spacer body 51 with no gap over the entire outer peripheral surface 51b in the circumferential direction without any gap. 55 (see FIG. 9). More specifically, the electric insulating film 55 is a part of the outer circumferential surface 50Ab of the insulating spacer main body 50A with a heater in a part in the axial direction (a part in the axial direction GH and a part in the circumferential direction CD). The first outer peripheral surface portion 50Ac) is entirely covered in the circumferential direction CD of the outer peripheral surface 50Ab of the insulating spacer main body portion 50A with a heater (see FIG. 9).

  In the first embodiment, as shown in FIG. 9, the electric insulating film 55 is provided so that the end of the front end GS of the electric insulation film 55 covers the end of the rear end GK of the heating sheet 52. The first and second terminal connecting portions 58 and 59 are partially covered without covering the first and second terminal connecting portions 58 and 59.

  Furthermore, at least a part (a part in the axial direction) of the inner peripheral surface 43c of the talc green compact 43 extends over the entire outer peripheral surface 50b of the insulating spacer with heater 50 in the circumferential direction CD. (Pressing contact) (see FIG. 11). More specifically, the entire inner peripheral surface 43c of the talc compact 43 extends over a part of the outer peripheral surface 55b of the electrical insulating film 55 in the axial direction over the entire outer peripheral surface 50b of the insulating spacer 50 with heater in the circumferential direction CD. In contact with the inner side DI (the left side in FIG. 11) in the direction. FIG. 11 is an enlarged view of a portion B in FIG.

  Thus, in the particle sensor 10 of the first embodiment, the inner peripheral surface 43c of the talc compact 43 extends over the entire outer circumferential surface 50b of the insulating spacer 50 with heater in the circumferential direction CD. There is no gap (specifically, between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 50b of the insulating spacer 50 with a heater) with respect to 50b (specifically, the outer peripheral surface 55b of the electric insulating film 55). The two can be brought into contact with each other so that there is no gap through which the gas to be measured passes in the axial direction GH. Therefore, the fine particle sensor 10 of the first embodiment uses the talc compact 43 so that the gas to be measured does not pass between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 50b of the insulating spacer 50 with heater. The inner peripheral surface 43c is a fine particle sensor in contact with the outer peripheral surface 50b of the insulating spacer 50 with a heater.

  Further, at least a part (a part in the axial direction) of the outer peripheral surface 43b of the talc compact 43 is in the circumferential direction CD of the inner peripheral surface 20c of the outer fitting 20 (specifically, the inner peripheral surface 21c of the mounting fitting 21). The entire surface is in contact (press-contact) with the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21) (see FIG. 11). Specifically, the entire outer peripheral surface 43b of the talc compact 43 extends over the entire outer circumferential surface CD of the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21). Of the inner peripheral surface 20c (more specifically, the inner peripheral surface 21c of the mounting bracket 21) is pressed in a manner of pressing a part of the inner peripheral surface 20c in the axial direction toward the radially outer DO (the right side in FIG. 11).

  Thus, the outer peripheral surface 43b of the talc compact 43 is spaced from the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21) in the entire circumferential direction CD without any gap (details). Between the outer peripheral surface 43b of the talc compact 43 and the inner peripheral surface 20c of the outer fitting 20 so that there is no gap through which the gas to be measured passes in the axial direction GH). it can.

  Therefore, the fine particle sensor 10 of the first embodiment uses the talc compact 43 interposed between the outer peripheral surface 50b of the insulating spacer 50 with the heater and the inner peripheral surface 20c of the outer fitting 20 to form the outer periphery of the insulating spacer 50 with the heater. A fine particle sensor is hermetically sealed (closed) between the surface 50b and the inner peripheral surface 20c of the outer fitting 20.

  In the particle sensor 10 according to the first embodiment, the electric insulating film 55 is formed of a sprayed electric insulating ceramic (specifically, alumina) film. Since the sprayed film of the electrically insulating ceramic is a dense ceramic film, the hermeticity between the sprayed film (the outer peripheral surface 55b of the electric insulating film 55) and the inner peripheral surface 43c of the talc compact 43 is contacted. (Sealability) is improved. This ensures that the gas to be measured flows between the inner peripheral surface 43c of the talc green compact 43 and the outer peripheral surface 50b of the insulating spacer with heater 50 (specifically, the outer peripheral surface 55b of the electric insulating film 55). It can be prevented from passing. Note that the electric insulating film 55 may be formed of an electric insulating glass film having heat resistance.

  In the particle sensor 10 according to the first embodiment, the thickness of the electric insulating film 55 is smaller than the thickness of the ceramic sheet 53. Therefore, the heat capacity of the insulating spacer with heater 50 can be reduced as compared with the case where the thickness of the electric insulating film 55 is equal to or greater than the thickness of the ceramic sheet 53. Therefore, in the fine particle sensor 10 of the first embodiment, in order to airtightly seal between the outer peripheral surface 50b of the insulating spacer 50 with the heater and the outer fitting 20, the outer peripheral surface 51b of the spacer main body 51 (the insulating spacer main body with the heater). Although the electric insulating film 55 is provided on the outer peripheral surface 50Ab) of the portion 50A, it is possible to suppress a decrease in the amount of heat generated in the insulating spacer 50 with a heater (a decrease in the rate of temperature rise of the gas contact portion 50S due to the heating of the heater 50B). it can.

  Further, in the fine particle sensor 10 of the first embodiment, the entire inner peripheral surface 43c of the talc compact 43 is in contact with the electric insulating film 55 (see FIG. 11). That is, all the portions of the outer peripheral surface 50b of the insulating spacer with heater 50 that come into contact with the inner peripheral surface 43c of the talc compact 43 are the outer peripheral surface 55b of the electric insulating film 55. By doing so, the film-like leads (the first heater lead 56 and the second heater lead 57) formed on the outer peripheral surface 51 b of the spacer body 51 come into contact with the talc compact 43. Can be prevented. Therefore, it is possible to prevent the lead portion (the first heater lead portion 56 and the second heater lead portion 57) from being damaged due to the contact with the talc compact 43.

  In the first embodiment, the electric insulating film 55 radially opposes not only the talc compact 43 but also the inner peripheral surface of the insulating holder 42 and the inner peripheral surface of the insulating sleeve 44 over the entire circumference thereof. (See FIGS. 2 and 4). This prevents the insulating holder 42 and the insulating sleeve 44 from coming into contact with the film-like leads (the first heater lead 56 and the second heater lead 57) formed on the outer peripheral surface 51b of the spacer body 51. it can. Therefore, troubles such as damage to the lead portions (first heater lead portion 56 and second heater lead portion 57) due to contact with the insulating holder 42 or the insulating sleeve 44 can be prevented.

  Further, a spacer heater connection terminal 91 provided at the end of a spacer heater lead wire 92 is joined to the first terminal connection portion 58 of the insulating spacer with heater 50 (see FIG. 4). As a result, the first terminal connection portion 58 of the insulating spacer with heater 50 and the spacer heater lead wire 92 are electrically connected. Further, a spacer heater connection terminal 93 provided at the tip of a spacer heater lead wire 94 is joined to the second terminal connection portion 59 of the insulating spacer with heater 50 (see FIG. 4). Thus, the second terminal connection portion 59 of the insulating spacer with heater 50 and the spacer heater lead wire 94 are electrically connected.

Further, the discharge element 60 is held in the insulating spacer with heater 50 via the protector 31, the conductive seal body 37, the second inner cylinder 38, the element holder 71 and the like.
Among them, the discharge element 60 has a base 60E made of an insulating ceramic, and a discharge electrode body 62 disposed inside the base 60E (see FIGS. 6 and 7). Among them, the discharge electrode body 62 has a discharge potential DV different from the sensor ground potential SGND (first potential) and the chassis ground potential CGND (ground potential).

  Further, the discharge element 60 has an element tip portion 60S which is located on the tip side GS and is arranged in the protector 31. The element tip portion 60S generates ions CP by discharging between the discharge electrode body 62 (specifically, the needle electrode portion 62D) and the protector 31, and charges the fine particles S in the gas SG to be measured. . Further, the discharge element 60 is located on the rear end side GK of the element tip section 60S, the discharge electrode body 62 (specifically, the discharge wiring 62L) is disposed inside, and the sealed section insulated from the outer surface 60CS. 60C (see FIGS. 2, 4, and 6).

  On the other hand, the protector 31 protects the element tip 60S of the discharge element 60 from water droplets and foreign substances, and also converts the gas to be measured SG, which is a part of the exhaust gas EG flowing through the exhaust pipe EP, into the element tip of the discharge element 60. It has a role to guide around 60S. The protector 31 has a cylindrical shape made of metal and is arranged on the tip side GS of the particle sensor 10. The protector 31 takes in the gas to be measured SG from the gas inlet 32I into its own internal space K and then discharges the gas from the gas outlet 32O. The portion of the protector 31 on the distal side GS is a tapered portion 32c having a tapered shape whose diameter decreases toward the distal side GS (see FIGS. 2 and 4).

  As shown in FIG. 3, the first inner cylinder 39 and the second inner cylinder 38 are integrally formed by swaging, and the cable connection portion 39C of the first inner cylinder 39 is connected to the outer conductor 82D. , The sensor ground potential SGND. The first inner cylinder 39 and the second inner cylinder 38 surround the element rear end side portion 60K of the discharge element 60 on the rear end side GK with respect to the sealed portion 60C (see FIGS. 2 and 4). Further, the conductive seal body 37 is made of conductive glass, is brought into contact with the second inner cylinder 38 and the protector 31 to conduct, and is in close contact with the outer surface 60CS of the sealed portion 60C of the discharge element 60 to discharge. The element 60 is hermetically sealed (see FIGS. 2 and 4).

  As described above, in the particle sensor 10, the conductive seal body 37 made of conductive glass is airtightly adhered around the outer surface 60CS of the sealed portion 60C of the discharge element 60. Therefore, the discharge element 60 is hermetically held by the conductive seal member 37 in the sealed portion 60C. In addition, the conductive seal body 37 is made of conductive glass, and conducts between the protector 31 and the second inner cylinder 38 at the sensor ground potential SGND via the first inner cylinder 39. Therefore, in order to set the protector 31 to the sensor ground potential SGND, a metal block-shaped member such as a metal shell that conducts between the first inner cylinder 39 or the second inner cylinder 38 and the protector 31 is not required, and the protector 31 is simple. Although having the configuration, the particle sensor 10 in which the discharge element 60 is held in an airtight manner can be provided.

  Next, the relationship between the insulating spacer with heater 50 and the conductive seal 37 will be described. The conductive seal body 37 made of conductive glass is airtightly adhered to the cylindrical inner peripheral surface 50c of the insulating spacer with heater 50 (see FIGS. 2 and 4). Then, through the conductive seal member 37, the distal end side portion 38S on the distal end side of the second inner cylinder 38, and the pipe rear end side portion 31K located on the rear end side GK of the protector 31, It is fixed to an insulating spacer 50 with a heater.

  As described above, in the particle sensor 10, the inner peripheral surface 50 c of the insulating spacer with heater 50 and the conductive seal member 37 are also in airtight contact with each other, and the seal between the discharge element 60 and the conductive seal member 37 is in phase. In addition, the inside of the insulating spacer with heater 50 can be hermetically sealed between the rear end side GK and the front end side GS by the conductive seal body 37. Moreover, the conductive seal member 37 allows the particle sensor 10 to have a simple configuration in which the distal end portion 38S of the second inner cylinder 38 and the rear end portion 31K of the protector 31 are fixed to the insulating spacer 50 with a heater. .

  More specifically, the insulating spacer with heater 50 has a stepped spacer step 50d that protrudes inward in the radial direction DI. On the other hand, among the substantially cylindrical protectors 31, the tube rear end portion 31K located on the rear end side GK has a stepped tube step portion 31KD in which the front end GS is smaller in diameter than the rear end GK. It has a tube rear end portion 31KK which is located on the rear end side GK with respect to the pipe step portion 31KD and includes an edge 31KF of the rear end side GK. The tube step 31KD of the protector 31 is locked to the spacer step 50d of the insulating spacer with heater 50 from the rear end GK to the front end GS. That is, the protector 31 is fixed to the insulating spacer with heater 50. In addition, the conductive seal member 37 is in close contact with the rear end portion 31KK of the rear end side portion 31K of the protector 31 from the rear end side GK, the radial inner DI, and the radial outer DO, and conducts to the protector 31. (See FIGS. 2 and 4).

  As described above, in the particle sensor 10, since the conductive seal member 37 is in contact with the rear end portion 31 KK of the protector 31, the protector 31 is reliably connected to the sensor ground potential SGND via the conductive seal member 37. It can be.

  The rectangular plate-like discharge element 60 is held by an element holder 71 made of insulating ceramic (see FIGS. 2 and 4). The element holder 71 has a stepped holder step 71D in which the diameter of the front end GS is smaller than that of the rear end GK on the outer peripheral surface 71R, and also has an insertion hole 71H through which the discharge element 60 is inserted. are doing. The element insertion portion 60P of the discharge element 60 is inserted into the insertion hole 71H. The element insertion portion 60 </ b> P is formed of a discharge element 60, which is an element distal end 60 </ b> S protrudingly arranged in the protector 31 at a position GS more distal than the element holder 71, and is surrounded by the conductive seal member 37 in an airtight manner. This is a portion located between the seal portion 60C and the seal portion 60C. The element insertion portion 60P of the discharge element 60 is held in the element holder 71 by the talc green compact 72 filled in the insertion hole 71H. The holder step 71D of the element holder 71 is locked to the tube step 31KD of the protector 31 from the rear end GK to the front end GS. In addition, the element holder 71 is in contact with the conductive seal member 37 from the tip side GS, and holds the conductive seal member 37.

  As described above, in the particle sensor 10, the holder step 71D of the element holder 71 is locked to the tube step 31KD of the protector 31. Since the pipe step 31KD of the protector 31 is locked to the spacer step 50d of the insulating spacer with heater 50, the element holder 71 is indirectly locked to the insulating spacer with heater 50. Moreover, since the element holder 71 is in contact with the conductive seal member 37 from the distal end GS, it is possible to reliably prevent the conductive seal member 37 from moving to the distal end GS within the insulating spacer 50 with a heater.

  In the particle sensor 10 of the first embodiment, the rectangular plate-shaped discharge element 60 is inserted into the insertion hole 71H of the element holder 71 made of insulating ceramic, and is inserted into the concave portion 71P having a larger diameter in the insertion hole 71H. The talc green compact 72 filled and compressed is fixed to the element holder 71 (see FIGS. 2 and 4). However, without using the talc compact 72, the recess 71P of the element holder 71 is filled with cement or solidified, and the recess 71P of the element holder 71 is also filled with the conductive glass forming the conductive seal body 37, The discharge element 60 may be fixed to the element holder 71 and the element holder 71 and the conductive seal 37 may be connected.

  Further, the first inner cylinder 39 and the second inner cylinder 38 are made of metal, and the second inner cylinder 38 has a bottomed cylindrical shape in which the distal end bottom portion 38SS of the distal side GS is closed. However, the tip bottom portion 38SS has an insertion hole 38SH through which the discharge element 60 is inserted (see FIGS. 2 and 4). Further, the second inner cylinder 38 surrounds the element rear end side portion 60K of the discharge element 60 from the radially outer side DO. The bottom end portion 38SS of the second inner cylinder 38 is in contact with the conductive seal member 37 from the rear end side GK.

  As described above, in the particle sensor 10, the first inner cylinder 39 and the second inner cylinder 38 have the second inner cylinder 38 including the bottom end portion 38SS, and the second inner cylinder 38 is located behind the discharge element 60. A Faraday cage can be configured by surrounding the end side portion 60K from the radially outer DO. In addition, since the distal end portion 38SS of the second inner cylinder 38 is in contact with the conductive seal body 37, the second inner cylinder and the conductive seal body 37 are appropriately conducted, and the conductive seal body 37 is connected to the sensor ground. The potential SGND can be used.

  An element sleeve 73 made of insulating ceramic is arranged in the distal end side portion 38S of the distal end side GS of the second inner cylinder 38, and is fixed by caulking the distal end side portion 38S (see FIGS. 2 and 4). . The discharge element 60 is also inserted through the insertion hole 73H of the element sleeve 73 and extends to the rear end side GK. The insulating spacer with heater 50 and the rear end side GK of the second inner cylinder 38 surround an element rear end side portion 60K of the discharge element 60, and include an outer separator 74 made of insulating ceramic, a lower separator 75, and an upper part. A separator 76 is provided.

  Of these, the outermost separator 74 on the most distal side GS extends to the second inner cylinder 38 in such a form that it is entirely inserted into the insulating spacer with heater 50 and the second inner cylinder 38. It is locked from the rear end side GK to the front end side GS by the insulating spacer 50 with a heater via 38. Further, each of the separators 74 to 76 is covered by the first inner cylinder 39 or the second inner cylinder 38 from the radially outer side DO, and the upper separator 76 located at the rearmost side GK is the first inner cylinder 39. At the rear end side GK (see FIGS. 2 and 4).

  The first inner cylinder 39 is provided with a tubular cable connecting portion 39C protruding to the rear end side GK, and the discharge potential cable 82 is inserted into the cable connecting portion 39C and is fixed by caulking. (See FIGS. 2 and 3). More precisely, the outer conductor 82D of the discharge potential cable 82 is electrically connected to the first inner cylinder 39 in the cable connection portion 39C of the first inner cylinder 39. Thereby, the first inner cylinder 39 is electrically connected to the first output terminal 111 of the ion source power supply circuit 110 of the control device 100 and the inner circuit case 170 via the outer conductor 82D of the discharge potential cable 82. Thus, the first inner cylinder 39, the second inner cylinder 38, the conductive seal body 37, and the protector 31 are all at the sensor ground potential SGND, and surround the discharge element 60 to form a Faraday cage.

  Next, the discharge element 60 will be described in detail. The discharge element 60 has a rectangular plate shape, and a discharge electrode pad 62P is formed on the first surface 60A (the upper surface in FIG. 6) on the rear end side GK from the center and on the front end GS than the center. A shield electrode pad 63P1 is formed. As shown in FIG. 3, a discharge potential lead wire 82L, which is a core wire of a discharge potential cable 82, is connected to the discharge electrode pad 62P via a discharge potential connection terminal 81. Thereby, the discharge electrode body 62 including the discharge electrode pad 62P is set to the discharge potential DV, and the conduction is controlled by the ion source power supply circuit 110 through the discharge potential cable 82 (see FIG. 8).

  On the other hand, the shield electrode pad 63P1 is formed so as to be located on the outer surface 60CS of the sealed portion 60C of the discharge element 60, and the conductive seal member 37 that is airtightly sealed around the outer surface 60CS. (See FIG. 2). Therefore, the shield electrode portion 63 including the shield electrode pad 63P1 is set to the sensor ground potential SGND.

  Element heater pads 64P1 and 64P2 are formed on the rear end GK of the second surface 60B (the lower surface in FIG. 6) of the discharge element 60 from the center (see FIG. 7). As shown in FIG. 3, element heater leads 84 and 86 are connected to the element heater pads 64P1 and 64P2 via element heater connection terminals 83 and 85, respectively. As a result, the element heater wiring 64 including the element heater pads 64P1 and 64P2 is energized and controlled by the element heater control circuit 150 through the element heater lead wires 84 and 86 (see FIG. 8).

  The discharge element 60 has flat ceramic layers 61A to 61E made of insulating ceramic and bonding layers 65A to 65D interposed therebetween and bonding the ceramic layers 61A to 61E to each other ( (See FIG. 7). Note that the base 60E is configured by these members.

  Of these, between the bonding layer 65A and the ceramic layer 61A, at a portion near the tip side GS, a substantially flat linear discharge wire 62L, and extending from the discharge wire 62L to the tip side GS, the discharge element A needle-like electrode portion 62D that protrudes in a needle shape from the element tip portion 60S of 60 is provided (see FIG. 7). The discharge wiring 62L is electrically connected to the outer surface of the ceramic layer 61A, that is, the discharge electrode pad 62P provided on the first surface 60A of the discharge element 60, through the discharge electrode via 62V provided on the ceramic layer 61A. As can be understood from FIGS. 6 and 7, the discharge wiring 62L of the discharge electrode body 62 is not exposed to the outer surface 60CS in the sealed portion 60C of the discharge element 60, and is inside the discharge element 60. positioned. Therefore, even if the conductive seal body 37 is formed in close contact with the outer surface 60CS, the discharge wiring 62L of the discharge electrode body 62 does not conduct to the conductive seal body 37 and is insulated from each other. .

  Further, between the ceramic layer 61E and the bonding layer 65D, two flat plate-shaped element heater leads 64L1 and 64L2 extending in the axial direction GH in parallel with each other, and a meander connecting these tip side GSs. An element heater section 64HT made of a wire in the shape of a circle is provided (see FIG. 7). The element heater lead wires 64L1 and 64L2 are respectively connected to element heater pads 64P1 and 64P2 provided on the outer surface of the ceramic layer 61E, ie, the second surface 60B of the discharge element 60, through element heater vias 64V1 and 64V2 provided on the ceramic layer 61E. Conducted. The element heater wiring 64 constituted by these elements prevents foreign particles such as soot from adhering to the element tip portion 60S of the discharge element 60 exposed to the gas to be measured SG, and removes the adhering foreign particles. In order to remove the element, the element tip 60S is provided to raise the temperature.

  The element heater pads 64P1 and 64P2 are in contact with element heater connection terminals 83 and 85 to which element heater lead wires 84 and 86 are connected (see FIG. 2). As described above, the element heater lead 86 is connected to the second output terminal 152 of the element heater control circuit 150, and is set to the chassis ground potential CGND. On the other hand, the element heater lead wire 84 is connected to the first output terminal 151 of the element heater control circuit 150, and is set to the element heater potential EHV (see FIG. 8). As can be easily understood from FIG. 7, the element heater lead wires 64L1 and 64L2 of the element heater wiring 64 are not exposed to the outer surface 60CS in the sealed portion 60C of the discharge element 60, and the Located inside. Therefore, even if the conductive seal body 37 is formed in close contact with the outer surface 60CS, the element heater lead wires 64L1 and 64L2 of the element heater wiring 64 do not conduct to the conductive seal body 37. Insulated.

  In addition, a flat plate-like shield electrode layer 63S is provided between the ceramic layer 61B and the bonding layer 65B at a position closer to the distal end GS (see FIG. 7). The shield electrode layer 63S is provided on the outer surface of the ceramic layer 61A, that is, the first surface 60A of the discharge element 60, through the shield electrode vias 63V2 and 63V1 and the shield electrode pads 63P3 and 63P2 provided in the ceramic layers 61B and 61A, respectively. To the shield electrode pad 63P1. The bonding layer 65A is provided with a through hole 65ATH including shield electrode pads 63P3 and 63P2 therein, so that the shield electrode pads 63P3 and 63P2 are in contact with each other to be conductive. For this reason, when the conductive seal body 37 is formed in close contact with the outer surface 60CS of the discharge element 60, the shield electrode pad 63P1 is electrically connected to the conductive seal body 37. Conduction to the conductive seal member 37 is made to be the sensor ground potential SGND.

As described above, in the particle sensor 10 of the first embodiment, the element heater wiring 64 for heating the element tip 60S is provided at the element tip 60S of the discharge element 60 exposed to the gas to be measured SG. . Note that one end (element heater pad 64P2) of the element heater wiring 64 is connected to the chassis ground potential CGND via the element heater lead wire 86.
However, when the element heater wire 64 is provided to heat the element tip portion 60S, the induced current flows through the element heater wire 64 due to the discharge at the discharge electrode body 62. Therefore, in the control device 100 (see FIG. 8) for controlling the particle sensor 10, the chassis ground potential CGND to which one end of the element heater wiring 64 (element heater pad 64P2) is connected fluctuates. Noise may be superimposed on a signal (output signal from the measurement control circuit 120).

  On the other hand, in the first embodiment, as can be easily understood from FIG. 7, the shield electrode layer 63S having the sensor ground potential SGND includes the discharge wire 62L of the discharge electrode body 62 and the element heater wire 64 of the element heater wire 64. It is interposed between the lead wires 64L1 and 64L2 and the element heater section 64HT, and electromagnetically shields between the discharge wiring 62L and the element heater lead wires 64L1 and 64L2 and the element heater section 64HT.

As a result, the induced current due to the discharge at the discharge electrode body 62 is suppressed from flowing through the element heater wiring 64, and the fluctuation of the chassis ground potential CGND and the output signal of the particle sensor 10 (the output from the measurement control circuit 120) Signal) is suppressed from being superimposed on noise.
In addition, the shield electrode layer 63S is electrically connected to the conductive seal body 37 to make the sensor ground potential SGND. More specifically, since the shield electrode pad 63P1 that conducts to the shield electrode layer 63S is provided on the outer surface 60CS of the sealed portion 60C, the shield electrode pad 63P1 easily conducts to the conductive seal body 37 and connects the shield electrode layer 63S to the sensor ground. It can be at the potential SGND. Therefore, it is not necessary to provide a wiring for supplying the sensor ground potential SGND to the shield electrode layer 63S of the discharge element 60 in the particle sensor 10 so that the shield electrode layer 63S is set to the sensor ground potential SGND.

Next, the structure of the protector 31 and the detection of the fine particles S by the fine particle sensor 10 will be described.
The protector 31 includes a cylindrical protector main body 32 having a narrowed distal end GS, and a plurality of (four in the first embodiment) trap members 33 to 36 housed in the protector main body 32 (in the first embodiment). 2 and 5). A plurality of gas inlets 32I are formed in the rear end side GK of the protector 31 (the protector main body 32) at equal intervals in the circumferential direction (see FIG. 5). The gas to be measured SG including the fine particles S is introduced into the inner space K of the protector 31 through the gas inlet 32I. The gas inlet 32I is located on the radially inner side DI of the cylindrical wall portion 21W of the mounting bracket 21 (see FIG. 2). Further, a gas outlet 320 for discharging the taken-in gas SG to be measured is formed at the tip of the protector 31 (the protector body 32). The gas outlet 320 is a circular opening whose center coincides with the axis AX of the particle sensor 10, and is provided at the tip of the protector 31.

  As shown in FIG. 12, in the protector 31 (the protector main body 32), the element tip 60S of the discharge element 60 protrudes into the internal space K on the tip side GS from the element holder 71. Therefore, when the corona discharge (air discharge) is generated between the needle electrode 62D and the protector 31, which is set to the sensor ground potential SGND, by setting the discharge potential DV to the discharge potential DV, oxygen ions and the like ionized in the internal space K are ionized. CP occurs. For this reason, when the gas to be measured SG flows through the internal space K, the ions CP adhere to the fine particles S in the gas to be measured SG, become charged fine particles SC, and are discharged from the gas outlet 32O to the exhaust pipe EP. The amount of electricity corresponding to the discharged ions CPH thus discharged is detected as the signal current Is.

  On the other hand, in order to suppress the discharge of the floating ions CPF that have not adhered to the fine particles S from the gas discharge port 320, the flow path of the gas to be measured SG flowing through the protector 31 is provided to the protector 31 by the trap members 33 to 36. Is a maze. Thereby, the floating ions CPF in the gas to be measured SG can be efficiently attached to the trap members 33 to 36 having the sensor ground potential SGND.

  That is, as can be understood from FIG. 5 and FIG. 12, the trap members 33 to 36 have the plate-like portions 33b, 34b, 35b, 36b in which one or a plurality of through holes 33d, 34d, 35d, 36d are perforated. ing. Moreover, the through holes provided in the adjacent trap members are arranged so as not to overlap in the axial direction GH. Therefore, as shown by the broken arrows in FIG. 12, when the gas to be measured SG flows through the through holes 33d, 34d, and 35d of the trap members 33 to 35, the gas to be measured SG is supplied to the trap members 34 to 36. Of the plate-like portions 34b, 35b, and 36b. For this reason, the floating ions CPF in the gas to be measured SG also easily collide with or be attracted to the plate-like portions 34b to 36b of the trap members 34 to 36 which are set to the sensor ground potential SGND, and the floating ions CPF are discharged from the gas outlet. Emission from 32O is suppressed.

  In the first embodiment, the “insulating spacer with heater 50” corresponds to the “insulating spacer” in the claims, the “spacer main body 51” corresponds to the “body part” in the claims, The first heater lead 56 and the second heater lead 57 "correspond to the" lead "in the claims.

(Example 2)
Next, a second embodiment of the present invention will be described with reference to the drawings. The particle sensor 210 and the particle detection system 201 according to the second embodiment are different from the particle sensor 10 and the particle detection system 1 according to the first embodiment only in the insulating spacer with heater (insulating spacer), and are otherwise the same ( See FIG. 15). Therefore, the following description focuses on differences from the first embodiment, and description of similar points is omitted or simplified.

  FIG. 13 is a longitudinal sectional view of the particle sensor 210 according to the second embodiment. FIG. 14 is an enlarged cross-sectional view of the particle sensor 210, and is a vertical cross-sectional view cut at a position shifted by 90 degrees around the axis from FIG. FIG. 15 is an exploded perspective view of the particle sensor 210. FIG. 16 is a perspective view of the insulating spacer with heater 250 (insulating spacer) according to the second embodiment. FIG. 17 is a perspective view of an insulating spacer main body 250A with a heater according to the second embodiment.

  As shown in FIGS. 13 to 16, the insulating spacer 250 with a heater according to the second embodiment has a cylindrical shape extending in the axial direction GH, and is interposed between the inner metal fitting 30 and the outer metal fitting 20 to form the inner metal fitting 30. And the outer fitting 20 are electrically insulated. The insulating spacer with heater 250 is located at the tip side GS of the insulating spacer with heater 250, a gas contact portion 250S that contacts the exhaust gas EG (gas to be measured), and a spacer heater that heats the gas contact portion 250S. 250B (more specifically, a heating resistor 254 described later).

  As shown in FIGS. 16 and 17, the insulating spacer 250 with a heater according to the second embodiment is formed in a cylindrical spacer main body 51 and a portion of the outer peripheral surface 51 b of the spacer main body 51 on the tip side GS in the axial direction GH. And a heat-generating resistor 254 in the form of a film. Further, the insulating spacer with heater 250 includes a film-shaped lead portion (the first heater lead portion 56 and the second heater lead portion 57) formed on the outer peripheral surface 51b of the spacer main body 51 and the outer peripheral surface 51b of the spacer main body 51. Of these, a film-shaped terminal connection portion (first terminal connection portion 58 and second terminal connection portion 59) formed at a portion on the rear end side GK in the axial direction GH is provided. The spacer body 51 is made of an electrically insulating ceramic (specifically, alumina) and has a cylindrical shape extending in the axial direction GH.

  The heating resistor 254 is formed of a film-like conductor, has a meandering (zigzag) shape, and has a form extending in the circumferential direction CD of the insulating spacer 250 with a heater. Among the heating resistors 254, the first connection portion 254b located on one side CD1 and the second connection portion 254c located on the other side CD2 are close to each other in the circumferential direction CD on the outer peripheral surface 51b of the spacer body 51. It is arranged. The first connection portion 54b is connected (electrically connected) to the tip of the first heater lead portion 56, and the second connection portion 54c is connected to the tip of the second heater lead portion 57. (Electrically connected). By causing the heating resistor 254 to generate heat, the gas contact portion 250S of the insulating spacer 250 with a heater can be heated. In the particle sensor 210 according to the second embodiment, the heating resistor 254 is disposed closer to the distal end GS than the insulating holder 42 in the axial direction GH (see FIGS. 13 and 14).

  Further, the first heater lead portion 56 is formed of a film-shaped conductor, and as shown in FIG. 14 and FIG. 17, the distal end thereof (the portion located on the distal side GS in the axial direction GH) is the first heater lead portion 56. It is connected to one connection portion 254b and has a shape extending to the rear end side GK in the axial direction GH. The second heater lead portion 57 is formed of a film-shaped conductor, and its tip (the portion located on the tip side GS in the axial direction GH) is connected to the second connection portion 254c of the heating resistor 254 as shown in FIG. Connected to form a shape extending toward the rear end side GK in the axial direction GH. The first heater lead portion 56 and the second heater lead portion 57 are separated from each other in the circumferential direction CD of the spacer body 51.

  The first terminal connection portion 58 is formed of a film-like conductor, and as shown in FIG. 14, is provided at a rear end portion 56b of the first heater lead portion 56 (a portion located on the rear end side GK in the axial direction GH). Connected. The second terminal connection portion 59 is made of a film-shaped conductor, and is connected to a rear end portion 57b (a portion located on the rear end side GK in the axial direction GH) of the second heater lead portion 57 as shown in FIG. ing.

  In the second embodiment, the heating resistor 254, the first heater lead 56, the second heater lead 57, the first terminal connection 58, and the second terminal connection 59 are connected to the outer peripheral surface 51 b of the spacer body 51. The upper part is formed integrally. Specifically, a conductor (metal fine particles) is printed in a film shape on the outer peripheral surface 51b of the spacer main body 51 by inkjet printing or tampo printing, so that the heating resistor 254, the first heater lead portion 56, and the second heater A lead portion 57, a first terminal connection portion 58, and a second terminal connection portion 59 are formed.

  Further, in the insulating spacer with heater 250 of the second embodiment, the heating resistor 254, the first heater lead portion 56 and the second heater lead portion 57, and the first terminal connection portion 58 and the second terminal connection portion 59 are used. And a spacer heater 250B. In addition, the spacer main body 51, the heating resistor 254, the first heater lead portion 56 and the second heater lead portion 57, and the first terminal connection portion 58 and the second terminal connection portion 59 form an insulating spacer body portion with a heater. 250A.

  In the particle sensor 210 according to the second embodiment, as described above, the insulating spacer with heater 250 has the spacer heater 250B (heating resistor 254) that heats the gas contact portion 250S. Therefore, even when foreign matter such as soot contained in the exhaust gas EG adheres to the gas contact portion 250S of the insulating spacer 250 with a heater, the electrical insulation between the inner metal fitting 30 and the outer metal fitting 20 is reduced. By heating the gas contact portion 250S by the heater 250B (heating resistor 254), foreign matter such as soot adhering to the surface of the gas contact portion 250S can be removed. As a result, the electrical insulation between the inner metal fitting 30 at the sensor ground potential SGND (first potential) and the outer metal fitting 20 at the chassis ground potential CGND (ground potential) is restored, and the exhaust gas EG in the exhaust gas EG is restored. It is possible to appropriately detect the amount of the fine particles.

  Further, in the particle sensor 210 of the second embodiment, the insulating spacer 250 with the heater covers at least a part of the outer peripheral surface 51b of the spacer main body 51 without any gap over the entire outer peripheral surface 51b in the circumferential direction. 255 (see FIG. 16). In detail, the electric insulating film 255 is formed in a part of the outer circumferential surface 250Ab of the insulating spacer main body 250A with a heater in the axial direction (a part in the axial direction GH and a part in the circumferential direction CD). The first outer peripheral surface portion 250Ac is covered without gaps over the entire outer peripheral surface 50Ab of the insulating spacer main body portion 50A with a heater in the circumferential direction CD (see FIG. 16). In the second embodiment, the electrical insulation film 255 does not cover the first terminal connection portion 58 and the second terminal connection portion 59, and the entire heating resistor 254, the first heater lead portion 56, and the second heater It covers a part of the lead portion 57.

  Furthermore, at least a part (part in the axial direction) of the inner peripheral surface 43c of the talc compact 43 extends over the entire outer peripheral surface 250b of the insulating spacer with heater 250 in the circumferential direction CD, and the outer peripheral surface 255b of the electric insulating film 255. (Pressing contact) (see FIG. 11). More specifically, the inner peripheral surface 43c of the talc compact 43 extends radially inward from the outer peripheral surface 255b of the electric insulating film 255 in a part of the outer peripheral surface 255b in the axial direction over the entire outer peripheral surface 250b of the insulating spacer 250 with heater. DI (left side in FIG. 11) in a pressing manner. FIG. 11 is an enlarged view of a portion C in FIG.

  Accordingly, in the fine particle sensor 210 of the second embodiment, the inner peripheral surface 43c of the talc compact 43 extends over the entire outer circumferential surface 250b of the insulating spacer 250 with heater in the circumferential direction CD. There is no gap (specifically, between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 250b of the insulating spacer 250 with a heater) with respect to 250b (specifically, the outer peripheral surface 255b of the electric insulating film 255). The two can be brought into contact with each other so that there is no gap through which the gas to be measured passes in the axial direction GH. Therefore, the fine particle sensor 210 of the second embodiment uses the talc compact 43 so that the gas to be measured does not pass between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 250b of the insulating spacer 250 with heater. The inner peripheral surface 43c of the above becomes a particle sensor in contact with the outer peripheral surface 250b of the insulating spacer 250 with a heater.

  Further, at least a part (a part in the axial direction) of the outer peripheral surface 43b of the talc compact 43 is in the circumferential direction CD of the inner peripheral surface 20c of the outer fitting 20 (specifically, the inner peripheral surface 21c of the mounting fitting 21). The entire surface is in contact (press-contact) with the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21) (see FIG. 11). Specifically, the entire outer peripheral surface 43b of the talc compact 43 extends over the entire outer circumferential surface CD of the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21). Of the inner peripheral surface 20c (more specifically, the inner peripheral surface 21c of the mounting bracket 21) is pressed in a manner of pressing a part of the inner peripheral surface 20c in the axial direction toward the radially outer DO (the right side in FIG. 11).

  Thus, the outer peripheral surface 43b of the talc compact 43 is spaced from the inner peripheral surface 20c of the outer bracket 20 (specifically, the inner peripheral surface 21c of the mounting bracket 21) in the entire circumferential direction CD without any gap (details). Between the outer peripheral surface 43b of the talc compact 43 and the inner peripheral surface 20c of the outer fitting 20 so that there is no gap through which the gas to be measured passes in the axial direction GH). it can.

  Accordingly, the fine particle sensor 210 of the second embodiment has a heater with the talc compact 43 interposed between the outer peripheral surface 250b of the insulating spacer 250 with the heater and the outer metal fitting 20 (the inner circumferential surface 21c of the mounting metal fitting 21). A particle sensor in which the space between the outer peripheral surface 250b of the insulating spacer 250 and the inner peripheral surface 20c of the outer fitting 20 is hermetically sealed (sealed).

  In the particle sensor 210 according to the second embodiment, the electric insulating film 255 is formed of a sprayed electric insulating ceramic (specifically, alumina) film. Since the thermal sprayed film of the electrically insulating ceramic is a dense ceramic film, the hermeticity between the thermal sprayed film (the outer peripheral surface 255b of the electrical insulating film 255) and the inner peripheral surface 43c of the talc compact 43 is improved. (Sealability) is improved.

  Further, in the particle sensor 210 according to the second embodiment, the heating resistor 254 is covered with the electric insulating film 255 without being exposed on the outer peripheral surface 250b of the insulating spacer 250 with a heater (see FIG. 16). This prevents foreign matter such as soot contained in the exhaust gas EG (gas to be measured) from adhering to the surface of the heating resistor 254 and around the heating resistor 254 when the particulate sensor 10 is used. In addition, it is possible to prevent the heating resistor 254 from being short-circuited through the foreign matter.

  In the particle sensor 210 according to the second embodiment, the thickness of the electric insulating film 255 is smaller than the thickness of the spacer body 51. Therefore, the heat capacity of the insulating spacer with heater 250 can be reduced as compared with the case where the thickness of the electric insulating film 255 is equal to or greater than the thickness of the spacer main body 51. Therefore, in the particle sensor 210 according to the second embodiment, the outer peripheral surface 51b of the spacer main body 51 (the insulating spacer main body with the heater) is required to hermetically seal the outer peripheral surface 250b of the insulating spacer 250 with the heater and the outer fitting 20 in an airtight manner. Although the electric insulating film 255 is provided on the outer peripheral surface 250Ab) of the portion 250A, it is possible to suppress a decrease in the amount of heat generated in the insulating spacer 250 with a heater (a decrease in the rate of temperature rise of the gas contact portion 250S due to the heating of the heater 250B). it can.

  Further, in the fine particle sensor 210 of the second embodiment, the entire inner peripheral surface 43c of the talc compact 43 is in contact with the electric insulating film 255 (see FIG. 11). That is, all the portions of the outer peripheral surface 250b of the insulating spacer with heater 250 that come into contact with the inner peripheral surface 43c of the talc compact 43 are the outer peripheral surface 255b of the electric insulating film 255. By doing so, the film-like leads (the first heater lead 56 and the second heater lead 57) formed on the outer peripheral surface 51 b of the spacer body 51 come into contact with the talc compact 43. Can be prevented. Therefore, it is possible to prevent a problem that the lead portions (the first heater lead portion 56 and the second heater lead portion 57) are damaged by the contact with the talc compact 43.

  In the second embodiment, the electric insulating film 255 radially opposes not only the talc compact 43 but also the inner peripheral surface of the insulating holder 42 and the inner peripheral surface of the insulating sleeve 44 over the entire circumference thereof. (See FIGS. 13 and 14). This prevents the insulating holder 42 and the insulating sleeve 44 from coming into contact with the film-like leads (the first heater lead 56 and the second heater lead 57) formed on the outer peripheral surface 51b of the spacer body 51. it can. Therefore, troubles such as damage to the lead portions (first heater lead portion 56 and second heater lead portion 57) due to contact with the insulating holder 42 or the insulating sleeve 44 can be prevented.

  In the above, the present invention has been described with reference to the first and second embodiments. However, the present invention is not limited to the first and second embodiments, and may be appropriately modified and applied without departing from the gist thereof. It goes without saying that you can do it.

For example, in the first and second embodiments, the entire inner peripheral surface 43c of the talc compact 43 extends over the entire outer peripheral surfaces 50b and 250b of the insulating spacers 50 and 250 with heaters in the circumferential direction CD. Are brought into contact with the outer peripheral surfaces 55b and 255b.
However, in the present invention, in order to prevent the gas to be measured from passing between the inner peripheral surface of the talc green compact and the outer peripheral surface of the insulating spacer with a heater, the inner peripheral surface 43c of the talc green compact 43 is required. At least a part thereof may be in contact with the outer peripheral surface of the electrical insulating film over the entire outer peripheral surface of the insulating spacer with heater in the circumferential direction CD.

  Specifically, for example, like the fine particle sensor 310 of Modification Example 1 shown in FIG. 18, the electric insulating film 355 having the length in the axial direction GH shorter than the talc compact 43 is used as the electric insulating film. It may be formed on the outer peripheral surface 51b of the main body 51. More specifically, a part of the inner peripheral surface 43c of the talc compact 43 in the axial direction (in the example shown in FIG. 18, the central part in the axial direction GH) is formed in the circumferential direction of the outer peripheral surface 350b of the insulating spacer with heater 350. The electric insulating film 355 is formed on the outer peripheral surface 51b of the spacer main body 51 so as to contact the outer peripheral surface 355b of the electric insulating film 355 (contact the outer peripheral surface 355b in a manner of pressing the radially inner side DI) over the entire CD. You may do it. FIG. 18 is a view corresponding to the B section enlarged view of FIG.

  Thus, a part of the inner peripheral surface 43c of the talc compact 43 in the axial direction is partially covered by the outer peripheral surface 350b of the insulating spacer with heater 350 over the entire circumferential direction CD of the outer peripheral surface 350b of the insulating spacer with heater 350. There is no gap between the outer peripheral surface 355b of a certain electric insulating film 355 and the outer peripheral surface 355b of the electric insulating film 355 between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 355b of the electric insulating film 355. (So that there is no gap through which the gas to be measured passes).

  Accordingly, the fine particle sensor 310 of the first modified example has the talc compact 43 so that the gas to be measured does not pass between the inner peripheral surface 43c of the talc compact 43 and the outer peripheral surface 350b of the insulating spacer 350 with a heater. The inner peripheral surface 43c is a particle sensor in contact with the outer peripheral surface 350b of the insulating spacer 350 with a heater. As a result, the talc compact 43 interposed between the outer peripheral surface 350b of the insulating spacer with heater 350 and the inner peripheral surface 20c of the outer metal fitting 20 causes the outer peripheral surface 350b of the insulating spacer with heater 350 and the inner circumference of the outer metal fitting 20 to move. It is possible to hermetically seal (close) the surface 20c.

1,201 Particle detection system 10, 210, 310 Particle sensor 20 Outer fitting 20c Inner peripheral surface 21 Mounting fitting (outer fitting)
21c Inner peripheral surface 30 Inner metal fitting 43 talc green compact (compact)
43c Inner peripheral surface 50, 250, 350 Heated insulating spacer (insulating spacer)
50b, 250b, 350b Outer peripheral surface 50A, 250A Heated insulating spacer body 50Ab, 250Ab Outer peripheral surface 50Ac, 250Ac First outer peripheral surface 50B, 250B Spacer heater (heater)
50S, 250S Gas contact part 51 Spacer body (body part)
51b Outer peripheral surface 52 Heating sheet 53 Ceramic sheet 53c Inner side surface 54,254 Heating resistor 55,255,355 Electrical insulating film 55b, 255b, 355b Outer peripheral surface 56 First heater lead portion (lead portion)
57 Second heater lead (lead)
58 First terminal connection part 59 Second terminal connection part 60 Discharge element 100 Control device AX Axis line CD Circumferential direction CP Ion DI Radial inside DO Radial outside EP Exhaust pipe (vent pipe)
EG exhaust gas (gas to be measured)
GH Axial direction direction GS Front end side GK Rear end side S Fine particles SC Charged fine particles CGND Chassis ground potential (ground potential)
SGND Sensor ground potential (first potential)

Claims (7)

A particle sensor extending from a front end side to a rear end side in an axial direction, wherein a part on the front end side of the particle sensor is attached to a ventilation pipe set to a ground potential through which a gas to be measured containing fine particles flows, and the measurement is performed. In a fine particle sensor for detecting the amount of the fine particles in the target gas,
A cylindrical outer fitting that is attached to the ventilation pipe and is set to the ground potential;
An inner metal fitting that is a first potential different from the ground potential and is surrounded by the outer metal fitting in a radial direction;
It has a cylindrical shape extending in the axial direction, is interposed between the inner metal fitting and the outer metal fitting and electrically insulates both, and has a gas contact portion that contacts the gas to be measured in its own axial direction. An insulating spacer on the tip side of
An annular green compact made of an electrically insulating powder, comprising a green compact interposed between an outer peripheral surface of the insulating spacer and an inner peripheral surface of the outer metal fitting,
The insulating spacer,
A cylindrical main body made of electrically insulating ceramic;
A heating sheet comprising: an electrically insulating ceramic sheet; and a film-shaped heating resistor formed on an inner surface of the ceramic sheet, wherein a portion of the outer peripheral surface of the main body portion on the tip side in the axial direction. A heating sheet that is wound around and heats the gas contact portion;
A film-shaped lead portion formed on the outer peripheral surface of the main body portion, the lead portion being connected to the heating resistor and extending toward the rear end side in the axial direction;
A film-shaped terminal connection portion formed on the outer peripheral surface of the main body portion and connected to a rear end portion of the lead portion;
An annular electrical insulating film that covers at least a part of the outer peripheral surface of the main body without a gap over the entire circumferential direction without covering the terminal connection part; And
The green compact is located on the rear end side of the heating sheet in the axial direction,
At least a part of the inner peripheral surface of the green compact is in contact with the electrical insulating film over the entire circumferential direction, and hermetically seals the gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. Particle sensor sealed. The particle sensor according to claim 1, wherein
A fine particle sensor in which the thickness of the electric insulating film is smaller than the thickness of the ceramic sheet. A particle sensor extending from a front end side to a rear end side in an axial direction, wherein a part on the front end side of the particle sensor is attached to a ventilation pipe set to a ground potential through which a gas to be measured containing fine particles flows, and the measurement is performed. In a fine particle sensor for detecting the amount of the fine particles in the target gas,
A cylindrical outer fitting that is attached to the ventilation pipe and is set to the ground potential;
An inner metal fitting that is a first potential different from the ground potential and is surrounded by the outer metal fitting in a radial direction;
It has a cylindrical shape extending in the axial direction, is interposed between the inner metal fitting and the outer metal fitting and electrically insulates both, and has a gas contact portion that contacts the gas to be measured in its own axial direction. An insulating spacer on the tip side of
An annular green compact made of an electrically insulating powder, comprising a green compact interposed between an outer peripheral surface of the insulating spacer and an inner peripheral surface of the outer metal fitting,
The insulating spacer,
A cylindrical main body made of electrically insulating ceramic;
A film-shaped heating resistor formed at a portion of the outer peripheral surface of the main body portion on the tip side in the axial direction, wherein the heating resistor heats the gas contact portion,
A film-shaped lead portion formed on the outer peripheral surface of the main body portion, the lead portion being connected to the heating resistor and extending toward the rear end side in the axial direction;
A film-shaped terminal connection portion formed on the outer peripheral surface of the main body portion and connected to a rear end portion of the lead portion;
An annular electrical insulating film that covers at least a part of the outer peripheral surface of the main body without a gap over the entire circumferential direction without covering the terminal connection part; And
At least a part of the inner peripheral surface of the green compact is in contact with the electrical insulating film over the entire circumferential direction, and hermetically seals the gap between the outer peripheral surface of the insulating spacer and the inner peripheral surface of the outer fitting. Particle sensor sealed. The particle sensor according to claim 3, wherein
A particle sensor, wherein the thickness of the electric insulating film is smaller than the thickness of the main body. The particle sensor according to claim 3 or 4, wherein
The fine particle sensor, wherein the heating resistor is covered with the electric insulating film without being exposed on an outer peripheral surface of the insulating spacer. The particle sensor according to any one of claims 1 to 5, wherein
The particle sensor, wherein the electric insulating film is a sprayed film of an electric insulating ceramic. The particle sensor according to any one of claims 1 to 6, wherein:
A particle sensor in which the entire inner peripheral surface of the green compact is in contact with the electrical insulating film.

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