JP2018136163A - Gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas sensor which is provided with a single heater, has the improved detection accuracy of a specific gas component, and which can materialize downsizing and power saving thereof.SOLUTION: The gas sensor is provided that comprises: an adjusting unit 10 which is provided with a first chamber C1 and a converting section 14 converting a first gas component into a second gas component; a sensor unit 20 which is provided with a second chamber C2 and a detecting section 24a with electric characteristics changing according to the concentration of the second gas component; a ceramic wiring board 50 on which the detecting section is disposed; and a single heater 24b. A through-hole 30 is formed in an area 50A in which the detecting section is disposed, of the ceramic wiring board, the through-hole is filled with a heat transfer material having high thermal conductivity. The adjusting unit and the heater are thermally coupled, also the sensor unit and the heater are thermally coupled, and the adjusting unit, the sensor unit, and the heater are integrated while at least a part of the heater is overlapped with the area when viewed from a direction in which the through-hole extends.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a gas sensor that detects the concentration of a specific gas component contained in a gas to be measured.

It is necessary to measure the NOx concentration in the gas to be measured for environmental management, process management, health management, and the like.
Therefore, a technique is known in which NO in the exhalation is converted to NO ₂ by a catalyst and then this NO ₂ is detected by a sensor element (Patent Document 1). In this technique, a conversion unit that performs pretreatment using a catalyst and a detection unit that includes a sensor element are formed separately, and are integrated into a single unit. Then, by providing heaters (heating resistors) separately for the conversion unit and the sensor element, the conversion unit and the sensor element are heated and stably operated.

US Patent Application Publication No. 2015/0250408 (FIG. 6B)

By the way, from the viewpoint of reducing the power consumption of the heater and reducing the size of the sensor, it is conceivable to heat the conversion unit and the detection unit with a single heater. In this case, for example, it is assumed that a heater is provided on the detection unit side mounted on the ceramic wiring board and the heat of the heater is transmitted to the conversion unit through the ceramic wiring substrate to heat the conversion unit and the detection unit.
However, since ceramic has low thermal conductivity, it is necessary to increase the amount of heat of the heater in order to transmit the heat of the heater to the conversion unit through the ceramic wiring board, and the power consumption of the heater increases. In addition, since the thermal conductivity of ceramic is low, the heat of the plate-like ceramic wiring board tends to dissipate in the direction of the plate surface. From this point also, the heat of the heater is difficult to be transmitted to the external conversion section, and the consumption of the heater Increases power.
Therefore, an object of the present invention is to provide a gas sensor that includes a single heater to improve the detection accuracy of a specific gas component, and that can achieve downsizing and power saving.

  In order to solve the above problems, the gas sensor of the present invention is provided with a first chamber for introducing the gas to be measured therein, and the first gas contained in the gas to be measured introduced into the first chamber. An adjustment unit including a conversion unit that converts a gas component into a second gas component, and a second chamber for introducing the gas to be measured that has passed through the adjustment unit are provided therein, and the second gas component A sensor unit having a detection unit whose electrical characteristics change according to the concentration of the ceramic unit, a ceramic wiring board in which the detection unit is arranged and at least a part of the sensor unit is housed in the sensor unit, the conversion unit, And a single heater for heating the detection unit, and in the region of the ceramic wiring board where the detection unit is arranged, in the thickness direction of itself At least one through hole is formed, and the through hole is filled with a heat transfer material having a higher thermal conductivity than the ceramic material constituting the ceramic wiring board, and the adjustment unit, the heater, and The adjustment unit, the sensor unit, and the heater are configured such that the sensor unit and the heater are respectively thermally coupled and at least a part of the heater overlaps the region when viewed from the extending direction of the through hole. Are integrated.

According to this gas sensor, the adjustment unit and the sensor unit need only be heated with a single heater, so that the configuration of the gas sensor can be simplified and the size of the gas sensor can be reduced compared to the case where the heaters are provided separately for both units. Can be realized.
Further, when the adjustment unit and the heater, and the sensor unit and the heater are respectively thermally coupled and viewed in the extending direction of the through hole, at least a part of the heater overlaps with the region. For this reason, between at least one of the units and the heater, the heat of the heater is easily transferred to the unit through a region (that is, a heat transfer material) having a higher thermal conductivity than the surrounding ceramic wiring board. Both units can be reliably heated with low power with a single heater.

In addition, by heating the detection unit of the sensor unit to the operating temperature in this way, the specific component can be detected stably, and the detection accuracy of the specific component can be improved.
Furthermore, by adjusting the numbers and diameters of the through holes and the heat transfer material, the thermal conductivity of the region can be easily controlled, and the amount of heat of the heater transmitted to both units can be easily adjusted. As a result, even with a single heater, the adjustment unit and the sensor unit can be easily controlled to different temperatures. In order to heat both units with a lower power with a single heater, it is preferable to provide a plurality of through holes.

In the gas sensor of the present invention, the thickness of the region may be smaller than the thickness of the ceramic wiring board adjacent to the region.
According to this gas sensor, since the thermal conductivity of the region is further increased, both units can be reliably heated with lower power with a single heater.

In the gas sensor according to the present invention, the main component of the ceramic material may be zirconia.
Since zirconia has a low thermal conductivity among ceramic materials, the heat of the heater is preferentially transmitted to areas with high thermal conductivity, and heat dissipation can be further suppressed in the direction of the surface of the ceramic wiring board, saving power. Can be realized even more.

In the gas sensor of the present invention, the heat transfer material may be nonconductive.
According to this gas sensor, since the non-conductive material has a high thermal conductivity, the heat of the heater is preferentially transmitted to the region having a high thermal conductivity, and the heat is dissipated in the direction of the surface of the ceramic wiring board. Further suppression can be achieved, and further power saving can be realized.

  According to the present invention, it is possible to obtain a gas sensor that can improve the accuracy of detection of a specific gas component and can achieve downsizing and power saving.

It is a disassembled perspective view of the gas sensor which concerns on embodiment of this invention. It is sectional drawing which follows the AA line of FIG. It is a partial section perspective view of a gas sensor concerning an embodiment of the present invention. It is a schematic diagram which shows the heat-transfer path | route from the heater in the gas sensor which concerns on embodiment of this invention. It is a fragmentary sectional view showing the modification of the gas sensor concerning the embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. 1 is an exploded perspective view of a gas sensor 1 according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, FIG. 3 is a partial sectional perspective view of the gas sensor 1, and FIG. It is a schematic diagram which shows a heat transfer path | route.
It is.
In FIG. 1, the gas sensor 1 includes an adjustment unit 10, a sensor unit 20, a pipe-shaped gas flow pipe 40, and a plate-shaped ceramic wiring substrate 50, and is formed in a box shape as a whole.

The adjustment unit 10 is formed in a substantially rectangular box shape with a flange and a metal case 12 having an upper surface (a surface facing upward in FIG. 1) and an adhesive (not shown) attached to the flange of the case 12. A rectangular frame-shaped packing 13 and a conversion portion 14 accommodated in the case 12. Then, the ceramic substrate 50 closes the opening of the case 12 by fixing the flange of the case 12 and the outer peripheral portion of the lower surface of the ceramic wiring substrate 50 to the frame of the packing 13 via an adhesive (not shown). The internal space of the case 12 forms the first chamber C1.
Pipe-shaped inlets 12a and outlets 12b serving as piping connection ports protrude from the lower surface of the case 12 apart from each other, and the inlets 12a and outlets 12b communicate with the first chamber C1.

Between the inlet 12a and the outlet 12b in the first chamber C1, a conversion unit 14 having a rectangular parallelepiped shape and porous and permeable to gas is disposed, and the surface of the first chamber C1 is disposed on the surface of the conversion unit 14. A sealing material 14a made of inorganic fiber (for example, alumina fiber) that seals the gap with the wall surface is provided.
And after the to-be-measured gas G introduced into the 1st chamber C1 from the inlet 12a contacts the conversion part 14, the 1st gas component contained in the to-be-measured gas G is converted into the 2nd gas component, Then, from the outlet 12b It is discharged outside the adjustment unit 10. The conversion unit 14 includes a catalyst such as zeolite supporting Pt that converts the first gas component (specifically NO) contained in the exhaled breath G into the second gas component (specifically NOx ₂ ).

  The sensor unit 20 includes a metal case 22 having the same or similar shape as the case 12 and having an open bottom surface, a rectangular frame-shaped packing 23 stacked on the flange of the case 22, and a sensor element unit housed in the case 22. 24, an adhesive layer 26 for bonding the sensor element portion 24 to a predetermined position (a recessed portion 50r described later) of the ceramic wiring substrate 50, and the ceramic wiring substrate 50. The flange of the case 22 and the outer peripheral portion of the upper surface of the ceramic wiring board 50 are fixed to the frame of the packing 23 via an adhesive (not shown), so that the ceramic wiring board 50 closes the opening of the case 22. The internal space of the case 22 forms the second chamber C2.

The sensor element portion 24 has a substantially rectangular plate shape, and as shown in FIG. 2, a detection portion 24a is disposed on the upper surface (surface facing upward in FIG. 1) side of the base portion 24c, and a single surface is formed on the lower surface side of the base portion 24c. One heater 24b is disposed, and the detection unit 24a and the heater 24b are integrated with each other on the top and bottom of the base unit 24c.
A concave portion 50r is formed in the center of the upper surface of the ceramic wiring substrate 50, and the sensor element portion 24 is arranged so that the heater 24b side is in contact with the concave portion 50r through the adhesive layer 26.
On the upper surface of the case 22, pipe-shaped inlets 22a and outlets 22b that serve as connection ports of the pipes are spaced apart from each other, and the inlets 22a and the outlets 22b communicate with the second chamber C2.

  The sensor element unit 24 is disposed between the inlet 22a and the outlet 22b in the second chamber C2 when viewed along the longitudinal direction of the ceramic wiring substrate 50, and the inlet 22a is connected to the outlet 12b through the gas flow pipe 40. Has been. Then, the gas G to be measured that has been converted to the second gas component through the adjustment unit 10 is introduced into the second chamber C2 from the inlet 22a through the gas flow pipe 40, and comes into contact with the detection unit 24a to be second. After the concentration of the gas component is measured, the gas component is discharged from the outlet 22b to the outside of the sensor unit 20.

The detection unit 24a detects the concentration of the second gas component by detecting an electrical signal that changes in electrical characteristics according to the concentration of the second gas component. The heater 24b heats the detection unit 24a to the operating temperature by energization heating. The output terminal of the detector 24a and the energization terminal of the heater 24b are electrically connected to the ceramic wiring board 50 by wire bonding (not shown).
The base portion 24c can be configured using, for example, an insulating ceramic substrate. Moreover, the detection part 24a can be made into the NOx sensor element which consists of a well-known mixed potential type sensor provided with the solid electrolyte body and a pair of electrode, for example. As the heater 24b, for example, a heating resistor composed of a meandering conductive pattern formed on the surface of the base portion 24c can be adopted.

  Here, the end portion 50e (left side in FIG. 1) of the ceramic substrate 50 is narrower than the cases 12 and 22, and extends to the outside of the cases 12 and 22 (left side in FIG. 1). On the front and back surfaces, there are a plurality of electrode pads 50p that are electrically connected to the detection unit 24a and the heater 24b through the wire bonding and wiring (lead conductor) formed on the surface of the ceramic wiring substrate 50. Has been placed. The electric signal output from the detection unit 24 is output to the outside through the electrode pad 50p of the ceramic wiring substrate 50, and the heater 24b is energized and heated by the electric power supplied from the outside through the electrode pad 50p.

Next, with reference to FIG. 3 and FIG. 4, the through hole and the heat transfer material 30 which are characteristic portions of the present invention will be described. In FIGS. 3 and 4, reference numerals are not assigned to the through holes in order to avoid complications, but it goes without saying that the outer edge portion of the heat transfer material 30 represents the wall surface of the through holes.
The sensor element unit 24 including the detection unit 24a is disposed in the central region 50A of the recess 50r of the ceramic wiring substrate 50. In the region 50A, a plurality of through-holes penetrating in the plate thickness direction (in FIG. 3, 4 × 8 × 32 in total) are formed, and each through-hole is filled with the heat transfer material 30. Yes.
The heat transfer material 30 has a higher thermal conductivity than the ceramic material constituting the ceramic wiring substrate 50. For example, in the present embodiment, the ceramic wiring board 50 is made of zirconia, and the main component of the ceramic material constituting the ceramic wiring board 50 is zirconia. The ceramic wiring substrate 50 may contain zirconia as a main component and a ceramic material as a subcomponent. The heat transfer material 30 is made of W (tungsten). W has higher thermal conductivity than zirconia.
For this reason, the thermal conductivity in the region 50A is higher than the thermal conductivity in the ceramic wiring substrate 50 adjacent to the region 50A. The ceramic wiring board 50 includes conductive members such as wiring (lead conductors), but these do not correspond to “a ceramic material constituting the ceramic wiring board 50”.

Examples of the heat transfer material 30 include metal materials such as Cu and W. The heat transfer material 30 can be formed by filling a paste containing these materials into a through hole opened in a green sheet of an unfired ceramic wiring board 50 and firing the ceramic wiring board 50 at the same time.
Moreover, the heat transfer material 30 can be made into the column shape about 0.1-0.5 mm in diameter, for example, and each heat transfer material 30 can be arrange | positioned at intervals of about 1 mm, for example.
Examples of the main component of the ceramic material constituting the ceramic wiring substrate 50 include zirconia, mullite, and alumina.

Here, as shown in FIG. 4, the sensor unit 20 and the heater 24 b are integrated by stacking and integrating the heater 24 b via the detection unit 24 a and the base unit 24 c in the sensor unit 20. It is thermally coupled like
On the other hand, when viewed from the stacking direction (direction in which the through hole extends), the heater 24b completely overlaps the region 50A. For this reason, the adjustment unit 10 and the heater 24b are integrated as shown in the arrow H2 by the heater 24b being laminated and integrated with the conversion unit 14 in the adjustment unit 10 via the adhesive layer 26 and the region 50A. Thermally coupled.
Note that “the sensor unit 20 and the heater 24b are thermally coupled” means that any member constituting the sensor unit 20 and the heater 24b are coupled without interposing air (without a gap), thereby conducting heat conduction. Means that is possible. The same applies to the meaning of “adjustment unit 10 and heater 24b are thermally coupled”.

As described above, the adjustment unit 10 and the sensor unit 20 need only be heated by the single heater 24b, so that the gas sensor 1 can be reduced in size and power can be saved as compared with the case where the heaters are separately provided in both units. .
Further, since the sensor unit 20 and the heater 24b are integrated, the heat of the heater 24b disposed in the sensor unit 20 is easily transmitted to the detection unit 24a as indicated by an arrow H1 in FIG.
Further, since the sensor unit 20 and the adjustment unit 10 are thermally coupled via the region 50A, the heat of the heater 24b passes through the region 50A having a higher thermal conductivity than the surrounding ceramic wiring substrate 50 as indicated by the arrow in FIG. It is easily transmitted to the adjustment unit 10 (converter 14) through H2. As a result, both units 10 and 20 can be reliably heated with low power by a single heater 24b.
Further, by heating the detection unit 24a of the sensor unit 20 to the operating temperature with the heater 24b in this way, the second gas component can be detected stably, and the detection accuracy can be improved.

Further, since the heat of the heater 24b is transmitted in the plate thickness direction through the region 50A having a high thermal conductivity, the rate of heat dissipation in the plate surface direction of the ceramic wiring board 50 is reduced, and the amount of heat of the heater 24b is effectively used. Thus, further power saving can be realized.
Furthermore, by adjusting the number and diameter of the through holes and the heat transfer material 30, the thermal conductivity of the region 50A can be easily controlled. For example, the heater 24b transmitted to the adjustment unit 10 (converter 14) by the arrow H2. The amount of heat can be adjusted easily.

As shown in FIG. 2, in the present embodiment, the heater 24b is plate-shaped, has a lower surface and an upper surface facing each other, the conversion unit 14 is disposed on the lower surface side, and the detection unit 24a is disposed on the upper surface side. Is arranged.
Thereby, since the conversion part 14 and the detection part 24a are each arrange | positioned on both surfaces of the heater 24b, the heat | fever of the heater 24b can be transmitted to the conversion part 14 and the detection part 24a without waste, and power saving can further be implement | achieved.
Further, a part of the constituent members for constituting the first chamber C1 of the adjustment unit 10 and a part of the constituent members for constituting the second chamber C2 of the sensor unit 20 are common ceramic members. Part 50r.
Thereby, the number of parts of the gas sensor 1A can be reduced by the ceramic thin plate portion 50r which is a common member, and the gas sensor 1A can be further downsized.

In the present embodiment, the thickness of the region 50A is thinner than the thickness of the ceramic wiring board 50 adjacent to the region 50A. Thereby, since the thermal conductivity of the region 50A is further increased, both the units 10 and 20 can be reliably heated with lower power by the single heater 24b.
Furthermore, in this embodiment, the main component of the ceramic material constituting the ceramic wiring substrate 50 (a component exceeding 50 mass% of the ceramic material) is zirconia. Since zirconia has a low thermal conductivity among ceramic materials, the heat of the heater 24b is preferentially transmitted to the region 50A having a high thermal conductivity, and heat dissipation in the direction of the plate surface of the ceramic wiring board 50 can be further suppressed. Power saving can be further realized.

  It goes without saying that the present invention is not limited to the above-described embodiment, but extends to various modifications and equivalents included in the spirit and scope of the present invention.

For example, as shown in FIG. 5, a heater 24b may be provided on the adjustment unit 10 side. In this case, contrary to the case of FIG. 4, the adjustment unit 10 and the heater 24b are thermally coupled as indicated by an arrow H2 by the heater 24b being laminated and integrated with the conversion unit 14 in the adjustment unit 10. doing.
On the other hand, when viewed from the stacking direction (direction in which the through hole extends), the heater 24b completely overlaps the region 50A. Therefore, the sensor unit 20 and the heater 24b are integrated by stacking and integrating the heater 24b with the detection portion 24a in the sensor unit 20 via the base portion 24c, the adhesive layer 26, and the region 50A. It is thermally coupled like

  Moreover, in the said embodiment, although the metal material (specifically W) was used as the heat-transfer material 30, the material of the heat-transfer material 30 is not limited to this. For example, a nonconductive material such as diamond or aluminum nitride may be used. Non-conductive materials tend to have high thermal conductivity and are insulative, so there is no possibility of short circuit between the wirings of the ceramic wiring board 50 due to the installation of the heat transfer material 30. Thus, even when the heat conductive material 30 is non-conductive, it is possible to heat both the adjustment unit 10 and the sensor unit 20 with lower power by the single heater 24b.

The gas sensor, the adjustment unit constituting the gas sensor, the shape of the sensor unit, and the like are not limited to the above embodiment. The types of the conversion unit and the detection unit are not limited.
The shape, number and diameter of the through holes and the heat transfer material are not limited.
Further, it is sufficient that at least a part of the heater 24b overlaps the region 50A when viewed from the direction in which the through hole extends, and the overlapping ratio is determined by the amount of heat generated by the heater 24b, the adjustment unit 10 (the conversion unit 14), and the sensor. It varies depending on the control temperature of the unit 20 (detector 24a). However, if the overlapping ratio is too small, the heat transmitted through the region 50A is reduced, so that 40% or more of the region 50A preferably overlaps, more preferably 100%.

DESCRIPTION OF SYMBOLS 1 Gas sensor 10 Adjustment unit 14 Conversion part 20 Sensor unit 30 Through hole, heat-transfer material 24a Detection part 24b Heater 50 Ceramic wiring board 50A area | region C1 1st chamber C2 2nd chamber G Gas to be measured

Claims (4)

A conversion chamber configured to convert a first gas component contained in the measurement gas introduced into the first chamber into a second gas component; An adjustment unit comprising,
A sensor unit provided with a detection unit in which a second chamber for introducing the gas to be measured that has passed through the adjustment unit is provided, and whose electrical characteristics change according to the concentration of the second gas component; ,
A ceramic wiring board in which the detection unit is arranged and at least a part of itself is housed in the sensor unit;
A single heater for heating the converter and the detector;
With
In the ceramic wiring substrate, at least one through hole penetrating in the plate thickness direction is formed in a region where the detection unit is arranged, and the ceramic material constituting the ceramic wiring substrate is formed in the through hole. Each of them is filled with a heat transfer material with a higher thermal conductivity than
The adjustment unit is configured such that the adjustment unit and the heater, and the sensor unit and the heater are respectively thermally coupled, and at least a part of the heater overlaps the region when viewed from the extending direction of the through hole. A gas sensor in which the sensor unit and the heater are integrated. The gas sensor according to claim 1,
The thickness of the said area | region is a gas sensor thinner than the thickness of the said ceramic wiring board adjacent to this area | region. The gas sensor according to claim 1 or 2,
A gas sensor in which the main component of the ceramic material is zirconia. It is a gas sensor as described in any one of Claims 1-3,
A gas sensor in which the heat transfer material is non-conductive.

Images