JP7459855B2 - Gas Detection Devices - Google Patents

Description

The technology disclosed in this specification relates to a gas detection device capable of detecting one or more gas components in a gas sample.

Patent Document 1 discloses a gas detection unit equipped with an adsorption section where a detectable gas is adsorbed and desorbed by temperature changes, and a detection section that detects the detectable gas desorbed from the adsorption section. A constant amount of detectable gas containing a low concentration of a component to be measured is allowed to flow, and the component to be measured is adsorbed by the adsorption section and concentrated. Next, the adsorption section is heated to desorb the component to be measured, and the desorbed gas is allowed to flow down the detection section.

Patent No. 62253569

In the technique of Patent Document 1, there is a difference in the distance to the detection section between the upstream side and the downstream side of the suction section. Then, a difference occurs in the arrival time to the detection section between the desorption gas from the upstream part of the adsorption part and the desorption gas from the downstream part, making efficient concentration difficult.

One embodiment of a gas sensing device disclosed herein includes a first chamber with a gas sample inlet and a first outlet. The gas detection device is placed inside the first chamber, and is capable of adsorbing a specific gas component in a gas sample, and is capable of desorbing the specific gas component adsorbed by being heated to a predetermined temperature or higher. Provide materials. The adsorbent has a membrane shape. The gas detection device includes a heater configured to be able to heat the adsorbent. The gas detection device includes a second chamber located adjacent to the first chamber and connected to the first chamber by a first communication path. The gas detection device is disposed inside the second chamber and includes a detection section capable of detecting a specific gas component desorbed from the adsorbent. The membrane surface of the adsorbent and the detection surface of the detection section are arranged to face each other via the first communication path.

Since the suction surface and the detection surface are arranged to face each other, the distance between the suction surface and the detection surface can be made approximately equal at any position within the surface. Since the time for the specific gas component separated from the adsorption surface to reach the detection surface can be made the same within the surface, efficient concentration of the specific gas component and improvement in detection sensitivity are possible.

The membrane surface of the adsorbent may be approximately parallel to a first direction, which is a direction from the inlet to the first outlet. The direction of the first communication passage may be approximately perpendicular to the first direction. Details of the effects will be explained in the examples.

The second chamber may include a second outlet disposed opposite to the first communication path. A detection unit may be disposed on a flow path from the first communication path to the second discharge port. The details of the effect will be explained in Examples.

The device may further include a switching unit that is connected to the first and second exhaust ports and selectively connects one of the first and second exhaust ports to the outside. Details of the effects will be explained in the examples.

The device may further include an opening/closing portion that can open and close the first communication passage. The opening/closing section closes the first communication passage when the first discharge port is connected to the outside, and opens the first communication passage when the second discharge port is connected to the outside. It may be configured such that this is possible. The details of the effect will be explained in Examples.

The first communication passage may have an opening. The opening/closing section may have a plate-like member. The plate-like member may be configured to be capable of changing between a state in which it contacts the entire outer periphery of the opening and a state in which it does not contact at least a part of the outer periphery of the opening. Details of the effects will be explained in the examples.

The adsorbent may be configured to allow gas to pass therethrough. The adsorbent may be arranged so as to block the communication path. The details of the effect will be explained in Examples.

The adsorbent may have a first surface that blocks the communication passage and a second surface opposite the first surface. The first surface may have a lower density than the second surface. Details of the effect will be explained in the examples.

1 is a schematic cross-sectional view of a gas detection system 1 of Example 1. FIG. 1 is a plan view of a gas detection system 1 of a first embodiment. FIG. 2 is a schematic cross-sectional view of a gas detection system 1a of Example 2. 4 is an enlarged top view of the opening/closing portion 51a. FIG. It is a sectional view of opening and closing part 51a. FIG. 5 is a cross-sectional view of the opening/closing part 52.

(Configuration of gas detection system 1)
FIG. 1 shows a schematic cross-sectional view of a gas detection system 1 of Example 1. FIG. 2 shows a plan view of the main body 5 viewed from the +z direction. Note that FIG. 1 is a cross-sectional view taken along the line II in FIG. 2. Furthermore, in FIG. 2, the gas passages 12 and 14, the adsorption chamber AC, the adsorbent 16, and the plurality of first communication passages 21 are shown by dotted lines.

The gas detection system 1 includes a gas detection device 2, a sample gas container 3, a pump 4, and a calculation device 7. The gas detection device 2 includes a main body 5 and a three-way valve 6. The sample gas container 3 is connected to the inlet 11 of the main body 5 via a pipe 61. The first outlet 13 and the third outlet 42 of the main body 5 are connected to the three-way valve 6 via piping 62 and 63. The outlet of the three-way valve 6 is connected to the pump 4 via a pipe 64.

The sample gas container 3 is a container for holding sample gas. The sample gas container 3 may be a pack made of resin film, for example. The three-way valve 6 is a valve that selectively connects one of the first outlet 13 and the third outlet 42 to the pump 4. The pump 4 is a part that generates a gas flow by suctioning. The calculation device 7 is a device that calculates the concentration of a specific gas component in the sample gas. The arithmetic device 7 may be connected to the detection units 31 to 33 by wiring (not shown). The arithmetic device 7 may be, for example, a PC.

(Configuration of main body 5)
The main body 5 has a structure in which the containers 10, 20, 30, and 40 are stacked and bonded to each other. The containers 10, 20, 30, and 40 may be bonded via a bonding layer (not shown). The container 10 has an adsorption chamber AC. An inlet 11 is formed at the −x-direction end of the container 10. The inlet 11 is connected to the adsorption chamber AC via a gas passage 12. As shown in FIG. 2, the gas passage 12 is branched. This allows the sample gas to be introduced uniformly into the y-direction width of the adsorption chamber AC. A first exhaust port 13 is formed at the +x-direction end of the container 10. The first exhaust port 13 is connected to the adsorption chamber AC via a gas passage 14. As shown in FIG. 2, the gas passage 14 is branched. This allows the sample gas to be uniformly discharged from the adsorption chamber AC.

The adsorbent 16 is disposed inside the adsorption chamber AC. The adsorbent 16 is capable of adsorbing specific gas components in the sample gas, and is capable of desorbing the adsorbed specific gas components by heating to a predetermined temperature or higher. The adsorbent 16 has a film shape and includes a lower surface 16L and an upper surface 16U opposite the lower surface 16L. The lower surface 16L is in contact with the bottom surface 20L so as to block the first communication passage 21. In other words, the film surface of the adsorbent 16 is approximately parallel to the direction from the inlet 11 to the first outlet 13 (the +x direction). Here, approximately parallel is a concept that includes not only completely parallel, but also a state in which the two are opposed to each other at an angle of about 30°.

A plurality of first communicating passages 21 are formed in the bottom surface 20L of the adsorption chamber AC. The plurality of first communication paths 21 extend in the z direction. That is, the direction of the first communicating path 21 (z direction) is substantially perpendicular to the direction from the inlet 11 to the first outlet 13 (+x direction). Here, the term "substantially perpendicular" is a concept that includes not only completely perpendicular, but also a state of being inclined at an angle of about 30 degrees with respect to the vertical direction.

The adsorbent 16 is configured to allow gas to pass therethrough. For example, it may be a porous body. This makes it possible to release the specific gas component separated from the adsorbent 16 to the back surface side (-z direction side) via the first communication path 21.

The adsorbent 16 also has a lower density on the bottom surface 16L side than on the top surface 16U side. For example, the porosity (proportion of the volume of space in the total volume of the material) of the bottom surface 16L in contact with the first communication passage 21 may be made larger than that of the top surface 16U (top surface). This makes it easier to release the desorbed specific gas components to the back surface side.

The adsorbent 16 is required to quickly desorb specific gas components in a direction approximately perpendicular to the membrane surface when heated, so it is preferable that the adsorbent 16 is as thin as possible. For example, the thickness of the adsorbent 16 may be 10 μm or less. The area of the adsorbent 16 may be 10 mm × 10 mm or less. This allows the main body 5 to be made smaller. Materials that can be used for the adsorbent 16 include mesoporous materials (e.g., mesoporous silica, mesoporous organic silica, mesoporous carbon, etc.), metal-organic frameworks (MOFs), zeolites, activated carbon, and other microporous materials.

A heater 15 is disposed on the upper surface of the container 10. The heater 15 is a member configured to be able to heat the adsorbent 16. As shown in Fig. 2, the heater 15 is disposed so as to at least partially overlap the adsorbent 16 in a plan view. The heater 15 is formed of a resistance heating element, and generates heat when electricity is applied. As the resistance heating element, for example, metals such as platinum, tungsten, tantalum, NiCr alloy, FeCrAl alloy, and CuNi alloy, and non-metals such as SiC, TiN, and _MoSi2 can be used.

A sensor chamber SC is formed in the containers 20 and 30. The sensor chamber SC is arranged below the adsorption chamber AC and adjacent to the adsorption chamber AC. The sensor chamber SC is connected to the adsorption chamber AC by a plurality of first communication passages 21.

Detection units 31-33 are arranged on the bottom surface 30L of the sensor chamber SC. That is, the film surface of the adsorbent 16 and the detection surfaces of the detection units 31-33 are arranged facing each other via the first communication passage 21. The detection units 31-33 are parts capable of detecting specific gas components desorbed from the adsorbent 16. The detection units 31-33 may be of different types. As the sensor of the detection unit, a sensor of a type in which the resistance, capacitance, resonant frequency, stress, etc. change due to the adsorption of the specific gas component can be used. The output of the detection units 31-33 is transmitted to the calculation device 7. The calculation device 7 calculates the concentration of the specific gas component from the sensor output.

A plurality of second exhaust ports 34 are formed in the bottom surface 30L of the sensor chamber SC. The plurality of second discharge ports 34 have openings on the side surfaces of the detection units 31 to 33. Then, they merge together, penetrate the bottom surface of the container 30 in the −z direction, and communicate with the discharge chamber EC. That is, the plurality of second discharge ports 34 are arranged to face the plurality of first communication passages 21. Detectors 31 to 33 are arranged on flow paths from the plurality of first communication passages 21 to the plurality of second discharge ports . Thereby, as will be described later, the specific gas component released from the plurality of first communication passages 21 can be efficiently exposed to the detection surfaces of the detection sections 31 to 33.

A discharge chamber EC is formed in the container 40. The discharge chamber EC is arranged below the sensor chamber SC and adjacent to the sensor chamber SC. A third outlet 42 is formed at the end of the container 40 in the +x direction. The third exhaust port 42 is connected to the exhaust chamber EC via a gas passage 43. The gas passage 43 may be branched, similar to the gas passage 12 and the gas passage 14.

(Method of manufacturing main body 5)
The main body 5 can be manufactured by micromachining technology. In the first step, each of the containers 10, 20, 30, and 40 is manufactured using a silicon wafer. For example, the plurality of first communicating paths 21 can be formed by reactive ion etching. In the second step, each of the detection parts 31 to 33, the adsorbent 16, and the heater 15 are formed. In the third step, the wafers on which the containers 10, 20, 30, and 40 have been made are integrated by wafer bonding. In the fourth step, the main body 5 is cut out from the bonded wafer.

The main body 5 can be manufactured using micromachining technology, making it possible to miniaturize the main body 5. This allows the gas detection device 2 to be made more compact.

(Gas detection operation of gas detection system 1)
First, an adsorption step is performed. The three-way valve 6 is switched so that the first outlet 13 is connected to the pump 4. When the suction operation of the pump 4 is started, the sample gas is introduced from the sample gas container 3 into the adsorption chamber AC through the inlet 11 and the gas passage 12. Since the first communicating path 21 is blocked by the adsorbent 16, the sample gas introduced into the adsorption chamber AC flows in the +x direction approximately parallel to the membrane surface of the adsorbent 16. (See dotted arrow Y1). That is, the adsorbent 16 also functions as a member that prevents the sample gas from flowing into the sensor chamber SC. By exposing the surface of the adsorbent 16 to the sample gas, the adsorbent 16 can selectively adsorb specific gas components. The sample gas that has passed through the adsorption chamber AC is exhausted by the pump 4 via the gas passage 14, the first exhaust port 13, the piping 62, and the three-way valve 6.

Next, a measuring step is performed. The three-way valve 6 is switched so that the third outlet 42 is connected to the pump 4. When the suction operation of the pump 4 is started, a flow path is formed from the lower surface 16L of the adsorbent 16 to the discharge chamber EC via the sensor chamber SC and the second discharge port 34 (see solid arrow Y2). At this time, a carrier gas such as N ₂ may be supplied from the inlet 11.

Then, heating of the adsorbent 16 by the heater 15 is started. When the adsorbent 16 is heated to a predetermined temperature or higher, specific gas components are separated from the adsorbent 16. The separated specific gas component is released from the lower surface 16L of the adsorbent 16 through the first communication path 21 in the −z direction, and is detected by the detection units 31 to 33.

The specific gas components that reach the detection units 31 to 33 are discharged into the discharge chamber EC via the second discharge port 34. The specific gas components in the discharge chamber EC are exhausted by the pump 4 via the gas passage 43, the third discharge port 42, the pipe 63, and the three-way valve 6.

(effect)
In the technology of the present specification, in the adsorption step, the sample gas can be made to flow approximately parallel to the film surface of the adsorbent 16. This allows the entire area of the adsorbent 16 from the end in the -x direction to the end in the +x direction to be evenly exposed to the sample gas, thereby improving the adsorption efficiency. As a result, the detection sensitivity of the gas detection system 1 can be improved, enabling detection of low concentration gases on the order of ppb.

In the technology of this specification, since the film surface of the adsorbent 16 and the detection surfaces of the detection units 31 to 33 are arranged to face each other, the distance between the two film surfaces can be adjusted at any position in the plane. They can be made almost equal. Since the time required for the specific gas component separated from the adsorbent 16 to reach the detection units 31 to 33 can be made the same within the plane, efficient concentration of the specific gas component is possible, and the detection by the gas detection system 1 is It becomes possible to increase sensitivity. Further, since a delay in the movement of the separated specific gas component can be prevented, the responsiveness of the detection units 31 to 33 can be improved. The response speed can be improved in detecting low concentration gas on the order of ppb.

When multiple detectors are arranged along the flow path of a specific gas component, there will be a time difference in the timing at which the multiple detectors are exposed to the specific gas component, resulting in differences in the responses of the multiple detectors. There are cases. In the technique of the present specification, since the plurality of detection units 31 to 33 are arranged perpendicularly to the flow path of the specific gas component, the plurality of detection units 31 to 33 can be exposed to the specific gas component at the same time. The responses of the plurality of detection units 31 to 33 can be made equal.

FIG. 3 shows a schematic cross-sectional view of the gas detection system 1a of Example 2. The gas detection system 1a of the second embodiment has a structure in which the gas detection system 1 of the first embodiment is turned upside down in the z direction. It also includes an opening/closing part 51a. Portions that are common between the gas detection system 1 of the first embodiment and the gas detection system 1a of the second embodiment are designated by the same reference numerals, and the description thereof will be omitted. Further, parts unique to the second embodiment are distinguished by adding "a" to the end of the reference numeral.

The adsorbent 16 is arranged on the bottom surface 20La of the adsorption chamber AC. The adsorbent 16 is placed apart from the first communication path 21a and does not block the first communication path 21a. Further, the density of the adsorbent 16 is lower on the upper surface 16U side than on the lower surface 16L side. For example, the porosity of the upper surface 16U (uppermost surface) may be made larger than that of the lower surface 16L. This makes it possible to easily release the separated specific gas component to the surface side.

A plurality of first communication passages 21a are formed on the upper surface 20Ua of the adsorption chamber AC. The plurality of first communication paths 21a extend in the z direction. Each of the plurality of first communication paths 21a is provided with an opening/closing portion 51a. The opening/closing part 51a is a part that can open and close the first communicating path 21a.

(Structure and operation of opening/closing unit 51a)
Fig. 4 shows an enlarged view of one opening/closing portion 51a. Fig. 4 is a top view seen from the +z direction. Figs. 5(A) and (B) are cross-sectional views taken along line V-V in Fig. 4. Fig. 5(A) shows the open state, and Fig. 5(B) shows the closed state.

The first communication passage 21a has an opening OP in the bottom surface 30La of the sensor chamber SC. The opening/closing part 51a has a plate-shaped member 51p, a beam 51b, and a base 51f. The base 51f is fixed to the bottom surface 30La. The beam 51b connects the base 51f and the plate-shaped member 51p. This supports the plate-shaped member 51p so that it can move in the z direction. An air vent VH is formed around the periphery of the plate-shaped member 51p. The plate-shaped member 51p and the container 20a are connected to a control circuit (not shown) so that a voltage can be applied.

The open state shown in FIG. 5(A) will be explained. When no voltage is applied between the plate-like member 51p and the bottom surface 30La, no electrostatic force is applied to the plate-like member 51p. The plate member 51p is separated from the bottom surface 30La. In other words, the plate member 51p is not in contact with at least a portion of the outer periphery of the opening OP. A flow path is formed from the opening OP to the sensor chamber SC via the vent VH.

The closed state shown in FIG. 5(B) will be explained. When a voltage is applied between the plate member 51p and the bottom surface 30La, an electrostatic attractive force acts between them. The beam portion 51b is deformed, and the plate member 51p moves in the -z direction. This brings the plate member 51p into contact with the entire outer periphery of the opening OP. The opening OP is closed by the plate member 51p, and the flow path from the adsorption chamber AC to the sensor chamber SC is blocked.

(Operation and Effects of Gas Detection System 1a)
In the adsorption step, a voltage is applied to the plate-like member 51p, and the plate-like member 51p is closed. The three-way valve 6 is switched so that the first outlet 13 is connected to the pump 4. The plate-like member 51p functions as a member that prevents the sample gas from flowing into the sensor chamber SC. Therefore, the sample gas introduced into the adsorption chamber AC flows in the +x direction, approximately parallel to the film surface of the adsorbent 16 (see the dotted arrow Y1a in FIG. 3). This can increase the adsorption efficiency.

In the measurement step, no voltage is applied to the plate-shaped member 51p, and the plate-shaped member 51p is in an open state. The three-way valve 6 is switched so that the third exhaust port 42 is connected to the pump 4. Since the first communication passage 21a is open, a flow path is formed from the adsorption chamber AC through the first communication passage 21a, the sensor chamber SC, and the second exhaust port 34a to the exhaust chamber EC (see the solid arrow Y2a). The specific gas component released from the adsorbent 16 by the heating of the heater 15 is released in a substantially vertical upward direction (+z direction) through the first communication passage 21a and is detected by the detection units 31 to 33. This enables efficient concentration of the specific gas component and improves the responsiveness of the detection units 31 to 33.

(Modification of the opening/closing portion 51a)
The opening/closing part 52 (FIG. 6) is a modified example of the opening/closing part 51a (FIG. 5). FIG. 6(A) shows the open state, and FIG. 6(B) shows the closed state. The opening/closing part 52 includes a plate-shaped member 52p and a fixing part 52f. The plate-shaped member 52p is a bimetal. An end part 52E of the plate-shaped member 52p is fixed to the bottom surface 30La by the fixing part 52f.

The open state shown in FIG. 6(A) will be explained. Simultaneously with the heating of the adsorbent 16 by the heater 15, the plate member 52p is also heated. Due to the heating, the plate-like member 52p is deformed so as to be warped in the +z direction, and is separated from the bottom surface 30La. The opening OP is opened, and a flow path is formed from the adsorption chamber AC to the sensor chamber SC via the first communication path 21a.

The closed state shown in FIG. 6(B) will now be described. When the plate-shaped member 52p is not heated, the plate-shaped member 52p has a straight shape. The plate-shaped member 52p is in contact with the entire outer periphery of the opening OP. The opening OP is blocked by the plate-shaped member 52p, and the first communication passage 21a is blocked.

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims as filed. Furthermore, the techniques illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives has technical utility in itself.

(Modification)
A plurality of adsorbents 16 may be disposed. Also, the types of adsorbents 16 may be different. For example, in the gas detection system 1 of FIG. 1, three types of adsorbents 16a to 16c may be disposed so as to face the detection units 31 to 33, respectively. This makes it possible to concentrate and detect three types of specific gas components. Also, the adsorbent 16a may be disposed so as to face the detection units 31 and 32, and the adsorbent 16b may be disposed so as to face the detection unit 33.

The number of detection units is not limited to three. Any number can be used depending on the object to be detected.

In the gas detection system 1 of FIG. 1, the adsorbent 16 may be arranged in various ways. For example, the adsorbent 16 may be arranged on the upper surface 20U of the adsorption chamber AC so that the first communication passage 21 is not blocked by the adsorbent 16.

The opening/closing portion 51a (FIG. 5) may be provided with a uniform height protrusion that surrounds the periphery of the opening OP. This makes it possible to prevent sticking of the plate-shaped member 51p to the bottom surface 30La due to electrostatic forces.

In the opening/closing section 52 (FIG. 6), there may be various heating methods for the plate member 52p. The plate-shaped member 52p may be heated by a control circuit (not shown) connected to the plate-shaped member 52p.

Adsorption chamber AC is an example of a first chamber. The sensor chamber SC is an example of a second chamber. The +x direction is an example of the first direction. The three-way valve 6 is an example of a switching section.

1: Gas detection system 2: Gas detector 3: Sample gas container 4: Pump 5: Main body 6: Three-way valve 10, 20, 30, 40: Container 11: Inlet 13: First exhaust port 15: Heater 16: Adsorbent 21: First communication passage 31-33: Detection section 34: Second exhaust port 42: Third exhaust port AC: Adsorption chamber SC: Sensor chamber EC: Exhaust chamber

Claims (7)

a first chamber having an inlet for the gas sample and a first outlet;
an adsorbent having a film shape, the adsorbent being disposed inside the first chamber and capable of adsorbing a specific gas component in the gas sample and desorbing the adsorbed specific gas component by being heated to a predetermined temperature or higher;
A heater configured to be able to heat the adsorbent;
a second chamber disposed adjacent to the first chamber and connected to the first chamber by a first communication passage;
a detection unit disposed inside the second chamber and capable of detecting the specific gas component desorbed from the adsorbent;
Equipped with
a film surface of the adsorbent and a detection surface of the detection unit are disposed opposite to each other via the first communication passage,
The adsorbent is configured to allow gas to pass therethrough,
The adsorbent is disposed so as to block the first communication passage.
Gas detection devices. The membrane surface of the adsorbent is substantially parallel to a first direction that is a direction from the inlet to the first outlet,
The gas detection device according to claim 1, wherein the direction of the first communication path is substantially perpendicular to the first direction. The second chamber includes a second exhaust port disposed opposite the first communication passage,
3. The gas detection device according to claim 1, wherein the detection portion is disposed on a flow path extending from the first communication passage to the second exhaust port. The gas detection device according to claim 3, further comprising a switching unit connected to the first exhaust port and the second exhaust port and selectively connecting one of the first exhaust port and the second exhaust port to the outside. further comprising an opening/closing part capable of opening and closing the first communication passage,
The opening/closing portion closes the first communication passage when the first discharge port is connected to the outside, and closes the first communication passage when the second discharge port is connected to the outside. The gas detection device according to claim 4, wherein the gas detection device is configured to be able to be brought into an open state. The first communication path includes an opening,
The opening/closing part includes a plate-like member,
The plate-like member is configured to be able to change between a state in which it contacts the entire outer periphery of the opening and a state in which it does not contact at least a part of the outer periphery of the opening. The gas detection device according to item 5. The adsorbent includes a first surface blocking the first communication path and a second surface opposite to the first surface,
The gas detection device according to claim 1 , wherein the first surface side has a lower density than the second surface side.

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