Gas Sensors

Abstract

This gas sensor comprises: a suction opening; a container that communicates with the suction opening; a gas sensor array provided on the inside of the container; and a suction unit provided to one end of the container. The suction unit is configured so as to perform: first suction in which a gas component within air is conveyed to the gas sensor array via the suction opening; and second suction in which the gas component is conveyed to the gas sensor array at a flow rate lower than the first suction. The suction unit is configured so as to perform the second suction concurrently with the first suction. The gas sensor array is configured so as to operate when the suction unit is performing the second suction.

Description

[Technical field]

[0001] The present disclosure relates to a gas sensor. More specifically, the present disclosure relates to a gas sensor including an aspirator that aspirates air containing at least a gas component to be detected. [Background technology]

[0002] Patent Document 1 discloses a combustible gas concentration measuring device that includes a gas intake means for intake of combustible gas, an air intake means for intake of air, a mixing section for mixing gas and air, a gas sensor for detecting the concentration of the gas, and a pump for supplying the gas to the gas sensor. In this gas sensor, gas present in a space to be detected is supplied to the gas sensor by the intake means and the pump, and the gas concentration can be detected by the gas sensor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2006-119061 A Summary of the Invention

[0004] The gas sensor includes a suction port, a container communicating with the suction port, a gas sensor array provided inside the container, and an aspirator provided at one end of the container. The aspirator is configured to perform a first suction for transporting a gas component in air to the gas sensor array via the suction port, and a second suction for transporting the gas component to the gas sensor array at a flow rate smaller than that of the first suction. The aspirator is configured to perform the second suction in superposition with the first suction. The gas sensor array is configured to operate when the aspirator is performing the second suction. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a cross-sectional view showing an overview of a gas sensor according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram for explaining the operating principle of the gas sensor of the above, and is a conceptual diagram showing the flow rate of air sent to the gas sensor array. [Diagram 3] FIG. 3 is a diagram for explaining the operating principle of the gas sensor of the above, and is a conceptual diagram showing the flow rate of air sent to the gas sensor array. [Figure 4] FIG. 4 is a diagram for explaining the operating principle of the gas sensor of the above, and is a conceptual diagram showing the flow rate of air sent to the gas sensor array. [Diagram 5] FIG. 5 is a plan view illustrating an overview of a gas sensor according to a modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] (1. Overview) The gas sensor 100 of this embodiment will be described below with reference to FIG. 1. However, the following embodiment is merely a part of various embodiments of the present disclosure. The following embodiment can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Also, each figure described in the following embodiment is a schematic diagram, and the size and thickness ratios of each component in the figure do not necessarily reflect the actual dimensional ratios.

[0007] The gas sensor 100 of this embodiment is configured to detect at least the target gas components, such as volatile organic compounds, when exposed to an atmosphere containing the target gas components, such as volatile organic compounds. The gas sensor 100 of this embodiment includes an intake port 10, a container 11, a gas sensor array 12, and an aspirator 13a. The aspirator 13a has at least one suction unit 13. The first suction is to draw the gas contained in the air into the gas sensor array 12 via the intake port 10. R The second suction transports the gas components contained in the air to the gas sensor array 12 at a flow rate smaller than that of the first suction. The suction unit 13 simultaneously performs the first suction and the second suction to overlap each other. The second suction operates the gas sensor array 12.

[0008] In this embodiment, the suction port 10 is connected to a container 11, and air containing volatile organic compounds is sucked into the container 11 through the suction port 10. A gas sensor array 12 is provided at one end of the container 11. The gas sensor array 12 detects the volatile organic compounds contained in the air. The air is sent to the container 11 through the suction port 10 by a suction unit 13.

[0009] The suction unit 13 sucks air from the suction port 10 in a space where the air to be detected exists. The gas components referred to in this disclosure may include, for example, odors emitted by living things, food, machines, and the human body, and gas components that are unpleasant to humans.

[0010] The suction unit 13, as a first suction, sucks in air that occupies most of the air transported from the outside of the gas sensor 100 to the gas sensor array 12 inside the container 11 through the suction port 10. Then, the gas components in the sucked air are detected by the gas sensor array 12.

[0011] The suction unit 13 delivers the gas components as the second suction at a flow rate smaller than that of the first suction to the gas sensor array 12. The second suction is superimposed on the first suction, thereby modulating the first suction.

[0012] The gas sensor array 12 has multiple types of gas sensor elements 12a that react differently to gas components, such as volatile organic compounds, and the multiple gas sensor elements 12a are arranged one-dimensionally, two-dimensionally, or three-dimensionally. In the gas sensor array 12 shown in FIG. 1, 16 types of gas sensor elements 12a are arranged two-dimensionally. The signal output from the gas sensor array 12 in response to the gas components forms a pattern in which the outputs of the multiple gas sensor elements 12a are arranged one-dimensionally, two-dimensionally, or three-dimensionally. The type and concentration of the gas components in the introduced air are detected by recognizing the formed pattern, for example, by a machine learning algorithm. The combination of volatile organic compounds in the introduced air is detected by recognizing the pattern.

[0013] The gas sensor 100 converts the reaction between the gas components and the individual gas sensor elements constituting the gas sensor array 12 into an electrical signal. The signal output from the gas sensor element can be largely influenced by the reaction with the gas components, particularly adsorption. The amount of adsorption n, which is the most important physical quantity in the adsorption phenomenon, is defined by the equilibrium temperature T and pressure P as n=F(P,T).

[0014] On the other hand, according to Bernoulli's theorem, mechanical energy is conserved in the relationship between the speed of a fluid, pressure, and the potential of an external force. Therefore, it is widely known that the signal output from the gas sensor element 12a varies depending on the speed of the fluid containing gas components, i.e., the flow rate. In other words, the signal output from the gas sensor element 12a can vary due to the air flow caused by the first suction as well as the second suction. The signal output from the gas sensor element 12a can vary due to the air pressure caused by the first suction as well as the second suction.

[0015] In addition, in this embodiment, the gas sensor array 12 uses a machine learning algorithm. It is generally known that the more the amount of learning data acquired in advance, the more likely the detection accuracy is to improve. The suction unit 13 conveys air to the gas sensor array 12 by the first suction. Furthermore, the second suction conveys air to the gas sensor array 12 at a flow rate smaller than that of the first suction, and by superimposing the second suction on the first suction. By adding a new air flow by the second suction in addition to the air flow by the first suction, many multiple patterns to be used as learning data can be generated even for air containing the same volatile organic compound. Compared to introducing air from the outside at a constant flow rate, there is an advantage that the detection accuracy of the volatile organic compound to be detected is easily improved. By adding a pressure change of the new air by the second suction in addition to the pressure change of the air by the first suction, there is an advantage that the detection accuracy of the volatile organic compound to be detected is easily improved even for air containing the same volatile organic compound.

[0016] (2.Details) The gas sensor 100 of this embodiment will be described in detail below. Figures 2 to 4 are explanatory diagrams of the operating principle of the gas sensor 100, and are conceptual diagrams showing the flow rate of air sent to the gas sensor array 12. The following description focuses on one gas sensor 100 in the gas sensor composed of multiple types of suction parts 13.

[0017] The suction port 10 is an opening that communicates between the atmosphere and the container 11. It is an opening for taking in air containing a volatile organic compound to be detected from outside the gas sensor 100 into the container 11. Although the number of suction ports 10 is one, the gas sensor 100 may have multiple suction ports 10 that each take in air from outside the gas sensor 100 into the container 11. The suction port 10 may be provided with an on-off valve or a flow control device that limits the flow rate.

[0018] The container 11 is a space that contains air containing volatile organic compounds. The container 11 is also a space for installing the gas sensor array 12 inside. The container 11 may be made of glass, engineering plastics, silicon, metal, carbon material, ceramics, or Teflon (registered trademark) to suppress adsorption of volatile organic compounds. The shape of the container 11 may be cylindrical, spindle-shaped, or rectangular. The volume of the container 11 is preferably 1000 mL or less, more preferably 100 mL or less, to efficiently exchange the air being transported.

[0019] The gas sensor array 12 includes multiple types of gas sensor elements 12a. The gas sensor elements are, for example, semiconductor sensors, electrochemical sensors, surface acoustic wave elements, field effect transistor biosensors (FET biosensors), chemical resistance change sensors, or optical sensors. In this embodiment, the gas sensor array 12 includes multiple gas sensor elements 12a having different detection characteristics. This allows pattern recognition using signals output from the gas sensor array 12 in response to volatile organic compounds. The gas sensor array 12 includes at least two or more types of gas sensor elements 12a. To facilitate signal processing, the gas sensor array 12 may include a power of two, for example, four, eight, or sixteen types of gas sensor elements 12a. The gas sensor array 12 may include multiple gas sensor elements 12a of the same type.

[0020] The suction section 13 includes an extension pump, a propeller pump, a viscous pump, a reciprocating pump, a rotary pump, a plunger pump, a gear pump, a screw pump, a vane pump, a centrifugal pump, a turbine pump, an axial flow pump, a mixed flow pump, a cascade pump, a diaphragm pump, a centrifugal fan, a sirocco fan, a paddle fan, a turbo fan, a mixed flow fan, an axial flow fan, and a cross flow fan.

[0021] A non-positive displacement pump capable of continuously transporting a large amount of air as the first suction can be used as the suction unit 13. By using a non-positive displacement pump, the kinetic energy of the rotating machine can be converted into the kinetic energy of the transport gas, so that the gas can be transported efficiently.

[0022] The suction unit 13 can use a positive displacement pump capable of quantitatively transporting a minute amount of air as the second suction. A positive displacement pump can directly convert mechanical energy into potential energy of the transport gas, and therefore has a high self-sufficiency. The suction unit 13 can combine a non-positive displacement pump and a positive displacement pump. It is preferable that the maximum discharge amount of the positive displacement pump performing the second suction is smaller than the maximum discharge amount of the non-positive displacement pump performing the first suction.

[0023] In order to prevent the volatile organic compounds from contaminating the inner surface of the suction part 13, it is preferable that the suction part 13 is provided downstream of the container 11. The suction part 13 may be provided inside the container 11 because it can efficiently transport air to the gas sensor array 12.

[0024] The suction unit 13 has a flow rate of preferably 10 L / min or less, more preferably 1 L / min or less, so as to transport a sufficient amount of volatile organic compounds to the gas sensor array 12. To shorten the detection time, the suction unit 13 has a flow rate that can replace almost all of the air present inside the container 11 in 1 minute or less. The suction unit 13 reduces the pressure of the container 11 to atmospheric pressure, i.e., 1.0×10 5 It is preferable that the pressure can be set to at least 10 Pa. The suction unit 13 can reduce the pressure inside the container 11 in order to obtain a greater number of patterns on the gas sensor array 12.

[0025] At least a part of the suction unit 13 can perform suction with less pulsation. By performing suction with less pulsation, another suction that overlaps can be effectively performed. Here, "less pulsation" means that the instantaneous flow rate shows a nearly constant value over time. For example, a multiple reciprocating pump can be used to reduce pulsation. Specifically, by using three diaphragm pumps and shifting the three eccentric axes by 120 degrees each, the suction waveform sucked from each pump can be made linear. An air chamber, i.e., a pulsation damper, can be used to reduce pulsation. An air chamber is a mechanism that uses the compressibility of the air in a container to suppress the pulsation of the reciprocating pump and create a stable gas flow.

[0026] The suction unit 13 may include a non-positive displacement axial fan. The axial fan continuously draws air by rotating an impeller, thereby suppressing pulsation.

[0027] The first suction refers to suctioning air that accounts for the majority of the air transported from the outside of the gas sensor 100 to the gas sensor array 12 provided inside the container 11 via the suction port 10. Figure 2 shows the change over time in the instantaneous flow rate at the position of the gas sensor array 12. The suction unit 13 suctions air at a flow rate V1 between time t1 and time t2 as the first suction. It is preferable that the flow rate V1 is constant.

[0028] The second suction refers to sucking in a portion of the air transported from the outside of the gas sensor 100 to the gas sensor array 12 provided inside the container 11 via the suction port 10. The suction unit 13 sucks in air as the second suction at a flow rate smaller than that of the first suction so as to be superimposed on the first suction. As shown in FIG. 2, the suction unit 13 superimposes a fluctuation in flow rate ΔV on the first suction between time t1 and time t2 as the second suction. The flow rate ΔV may have a constant period with respect to time (see FIG. 2) since gas can be easily detected by the flow rate ΔV. The flow rate ΔV may have an irregular period with respect to time. In the second suction flow rate ΔV may be constant or may vary.

[0029] The waveform of the second suction may be a triangular wave as shown in Fig. 2, or a sine wave as shown in Fig. 3. As shown in Fig. 3, in a part of the section in which the first suction is performed from time t3 to time t6, the second suction may be performed from time t4 to time t5. The second suction has a flow rate ΔV that changes monotonically from time t1 to time t2 as shown in Fig. 4. The second suction may have a flow rate ΔV that increases or decreases monotonically.

[0030] The flow rate V1 sucked in as the first suction is smaller than the flow rate ΔV sucked in as the second suction. By setting the ratio ΔV / V1 of the flow rate ΔV to the flow rate V1 to be 3 or more, a pattern can be easily obtained from the gas sensor array 12. The flow rate V1 is set so that just the right amount of air can be sucked into the container 11 and transported to the gas sensor array 12.

[0031] (3.Operation) An example of the operation of the gas sensor 100 of this embodiment, that is, a series of steps in the gas detection method, will be described below with reference to Fig. 2. First, the gas sensor 100 starts performing the first suction at time t1 after preparing the gas sensor 100 for operation. After starting the first suction, the gas sensor 100 starts performing the second suction. The first suction and the second suction may start simultaneously.

[0032] Thereafter, while the second suction is being performed, the gas sensor array 12 detects volatile organic compounds contained in the air at the measurement point 20a shown in FIG. 2. While the second suction is being performed, the gas sensor array 12 detects volatile organic compounds at a plurality of measurement points 20a, 20b, 20c, and 20d. There are at least two measurement points. As shown in FIG. 2, at the plurality of measurement points 20a, 20b, 20c, and 20d, patterns 21a, 21b, 21c, and 21d are obtained from the gas sensor array 12. In the patterns 21a, 21b, 21c, and 21d shown in FIG. 2, black dots indicate gas sensor elements 12a that are reacting to gas components and outputting signals, and white dots indicate gas sensor elements 12a that are not reacting to gas components and outputting no signals.

[0033] A "pattern" in this disclosure is a set of responses of a plurality of gas sensor elements 12a constituting the gas sensor array 12. The patterns 21a, 21b, 21c, and 21d are different from each other depending on the flow rate. Some of the patterns 21a, 21b, 21c, and 21d may be the same as each other. The response of the gas sensor element 12a may be a response in an equilibrium state or a response in a transient state.

[0034] Next, the second suction is ended. Then, the first suction is ended. The first suction and the second suction may be ended simultaneously.

[0035] In this embodiment, it is possible to detect volatile organic compounds contained in the air by separating the first suction and the second suction. Therefore, while air is being sucked into the container 11 by the first suction, it is easy to detect volatile organic compounds contained in the air sucked by the second suction.

[0036] (4. Modifications) The above-described embodiment is merely one of various embodiments of the present disclosure. The above-described embodiment can be modified in various ways depending on the design and the like as long as the object of the present disclosure can be achieved. Modifications of the above-described embodiment are listed below. The modifications described below can be applied in appropriate combination. FIG. 5 is a plan view showing an outline of a gas sensor 100a according to a modification of an embodiment of the present disclosure. In FIG. 5, the same reference numerals are used for the same parts as those of the gas sensor 100 shown in FIG. 1.

[0037] In the gas sensor 100a according to the present disclosure, the aspirator 13a includes a plurality of aspirating units 13. The plurality of aspirating units 13 are connected to the container 11 via flow paths 13b communicating with each other. An opening / closing valve or a flow rate control device may be provided in the flow path 13b.

[0038] As shown in FIG. 5, the gas sensor 100a includes a suction control unit 14 that controls the plurality of suction units 13. The suction control unit 14 controls the state of the suction units 13 by providing a suction control signal to the suction units 13. In this embodiment, the suction control unit 14 controls the plurality of suction units 13 so that both the first suction and the second suction are in an operating state at a predetermined time. The suction control unit 14 may control the execution of the first suction and the second suction by providing a suction control signal to one of the plurality of suction units 13. For example, the suction control unit 14 may control the plurality of suction units 13 so that one suction unit 13 performs the first suction with a constant flow rate and the other suction unit 13 performs the second suction with a varying flow rate that modulates the first suction.

[0039] The gas sensor 100a has a sensor control unit 15. The sensor control unit 15 controls the state of the gas sensor array 12 by providing a sensor control signal to the gas sensor array 12. The sensor control unit 15 may receive an output signal from the gas sensor array 12. The sensor control unit 15 may be provided with a storage unit. The storage unit includes an electrically rewritable non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory) and a volatile memory such as a RAM (Random Access Memory). The storage unit stores the output signal from the gas sensor array 12, the operation of the suction unit 13, the flow rate at the position of the gas sensor array 12, information on the state of the air in the container 11, such as temperature, pressure, and humidity, and information indicating the type and concentration of the detected volatile organic compound at predetermined intervals.

[0040] The gas sensor 100a may be provided with a flow rate detector. The flow rate detector may be provided at one end of the suction port 10, the container 11, or the suction part 13.

[0041] 5, the gas sensor array 12 may be provided at a position offset from the center position 11c of the container 11. The gas sensor array 12 may be provided at a position offset from a line connecting the end face of the suction port 10 on the container 11 side and the end face of the suction part 13 on the container side. In a gas sensor 100 having a plurality of suction parts 13, the gas sensor array 12 may be provided near one of the suction parts 13.

[0042] The suction unit 13 may suck in a comparison gas to compare with air containing a volatile organic compound to be detected. The "comparison gas" in the present disclosure may be a gas obtained by passing the sucked air through a filter, or may be a gas obtained by sucking through the suction port 10. The "comparison gas" in the present disclosure may be a gas stored in a cylinder in advance. The comparison gas may be, for example, purified air, nitrogen gas, or helium gas. The suction unit 13 may suck in the comparison gas by the first suction and the second suction. The gas sensor array 12 may obtain a pattern for the comparison gas sucked in by the first suction and the second suction. The gas sensor array 12 may detect a volatile organic compound contained in the comparison gas sucked in by the first suction and the second suction.

[0043] (5. Summary) As described above, the gas sensor according to the first aspect includes an intake port, a container, a gas sensor array, and an intake unit. The intake unit operates the gas sensor array by superimposing a first intake for transporting a gas component in the air to the gas sensor array through the intake port and a second intake for transporting the gas component to the gas sensor array at a flow rate smaller than that of the first intake.

[0044] This embodiment has the advantage that it is easy to improve the detection accuracy of the gas components to be detected, i.e., the volatile organic compounds.

[0045] In the gas sensor according to the second aspect, the suction portion is provided in a plurality of locations, and the second suction is performed by at least one of the plurality of suction portions.

[0046] According to this aspect, since at least one suction portion can form a flow rate smaller than that of the first suction, there is an advantage that air can be easily sucked in.

[0047] In the gas sensor according to the third aspect, the gas sensor array obtains a plurality of patterns for the gas components contained in the air sucked in by the second suction.

[0048] According to this aspect, the gas sensor array has an advantage that the detection accuracy can be improved since a plurality of patterns can be obtained.

[0049] In the gas sensor according to the fourth aspect, the suction control unit that controls the operating state of the suction unit supplies a signal to the sensor control unit that controls the gas sensor array.

[0050] According to this aspect, there is an advantage that a pattern reflecting the operating state of the suction part can be efficiently acquired by the gas sensor array.

[0051] In the gas sensor according to the fifth aspect, the suction section suctions air containing a gas component and a comparison gas used for comparison with the air.

[0052] According to this embodiment, since the gas component can be detected based on the reference gas, there is an advantage that the detection accuracy can be improved.

[0053] The configurations according to the second to fifth aspects are not essential for the gas sensor and may be omitted as appropriate. [Industrial Applicability]

[0054] The gas sensor of the present disclosure is useful for detecting various gases or odors. [Explanation of symbols]

[0055] 100 Gas Sensor 10 Suction port 11 Container 12 Gas Sensor Array 13 Suction part 14 Suction control unit 15 Sensor control unit 20a,20b,20c,20d measurement points Patterns 21a, 21b, 21c, 21d

Claims

1. A suction port; A container communicating with the suction port; a gas sensor array disposed within the vessel; an aspirator provided at one end of the container; Equipped with The aspirator comprises: a first suction for conveying a gas component in the air to the gas sensor array through the suction port; a second intake for delivering a gas component to the gas sensor array at a flow rate less than that of the first intake; The device is configured to: the aspirator is configured to periodically vary a flow rate at the position of the gas sensor array by performing the second suction superimposed on the first suction; The gas sensor array is configured to operate when the aspirator is performing the second suction.

2. The aspirator comprises: A first suction unit configured to perform the first suction; A second suction unit configured to perform the second suction; The gas sensor according to claim 1 , comprising:

3. The first suction section is a non-positive displacement pump, The second suction unit is a positive displacement pump.

3. The gas sensor according to claim 2.

4. The gas sensor array includes a plurality of gas sensor elements. the gas sensor array obtains a plurality of patterns each indicating one or more gas sensor elements that react to a gas component contained in the air sucked by the second suction, among the plurality of gas sensor elements; The gas sensor according to claim 1 .

5. Detecting volatile organic compounds based on the plurality of patterns acquired by the gas sensor array.

5. The gas sensor according to claim 4.

6. a sensor controller configured to control the gas sensor array; a suction controller configured to control an operating state of the aspirator and provide a signal to the sensor controller; The gas sensor according to claim 1 , further comprising:

7. 7. The gas sensor according to claim 1, wherein the aspirator is configured to aspirate the air containing the gas component and a reference gas used for comparison with the air.

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